This is a Mogre version of Raycasting to the polygon level as ported by Funguine (ketarax on #ogre3d) & Antont.

Here is the forum thread of the original code (C++).

Introducion

An Ogre ray query generally only detect bounding boxes (-AABBs), like you see on this image. With this code you can avoid this disadvantage.
Rays_and_BoundingBox_1a.gif

Important note

This code only returns correct results for polygons defined by rendertype OT_TRIANGLE_LIST. If a mesh contains other rendertypes (different triangle definition), lines or points, you will get wrong results or even a crash. Terrain and ManualObject aren't supported. Also it's not recommend for heavy usage (multiple queries per second). For details look here.

An improved alternative

Because of disadvantages with the code on this wiki page, user Beauty wrotes a new polygon raycasting class from scratch.
In general the code is ready to use. Only some helper classes (e.g. for debugging) are added quick and dirty to a second code file. In the future Beauty wants to polish up the code and publish it in a common way later (not only as attachment of a forum post).

The (alternative) polygon raycasting code you find here in the forum. Notes about you find here.
For questions about Beautys code, please us the same forum topic.

Note: The code on this wiki page (below this section) is the old and "primitive" polygon raycasting version.

Code for initialization

Define this field (variable) in your class

RaySceneQuery m_pray_scene_query;


Initialize it, for example in CreateScene()

// create the ray scene query object
m_pray_scene_query = sceneMgr.CreateRayQuery(new Ray(), SceneManager.WORLD_GEOMETRY_TYPE_MASK);
if (null == m_pray_scene_query)
{
    return false;
}
m_pray_scene_query.SetSortByDistance(true);

Method for raycast

// raycast from a point in to the scene.
// returns success or failure.
// on success the point is returned in the result.
public bool RaycastFromPoint(Vector3 point, Vector3 normal, ref Vector3 result,
    ref Vector3 resNormal)
{
    // create the ray to test
    Ray ray = new Ray(point, normal);

    // check we are initialised
    if (m_pray_scene_query != null)
    {
        // create a query object
        m_pray_scene_query.Ray = ray;

        // execute the query, returns a vector of hits
        RaySceneQueryResult rayresult = m_pray_scene_query.Execute();
        if (rayresult.Count <= 0)
        {
           // raycast did not hit an objects bounding box
            return false;
        }
    }
    else
    {
        return false;
    }

    // at this point we have raycast to a series of different objects bounding boxes.
    // we need to test these different objects to see which is the first polygon hit.
    // there are some minor optimizations (distance based) that mean we wont have to
    // check all of the objects most of the time, but the worst case scenario is that
    // we need to test every triangle of every object.
    float closest_distance = -1.0f;
    Vector3 closest_result = Vector3.ZERO;
    Vector3 vNormal = Vector3.ZERO;
    RaySceneQueryResult query_result = m_pray_scene_query.GetLastResults();

    foreach (RaySceneQueryResultEntry this_result in query_result)
    {
        // stop checking if we have found a raycast hit that is closer
        // than all remaining entities
        if ((closest_distance >= 0.0f) &&
            (closest_distance < this_result.distance))
        {
            break;
        }

        // only check this result if its a hit against an entity
        if ((this_result.movable != null) &&
            (this_result.movable.MovableType == "Entity"))
        {
            // get the entity to check
            Entity pentity = (Entity)this_result.movable;

            // mesh data to retrieve 
            uint vertex_count = 0;
            uint index_count = 0;
            Vector3[] vertices = new Vector3[0];
            UInt64[] indices = new UInt64[0];

            // get the mesh information
            GetMeshInformation(pentity.GetMesh(),
                ref vertex_count, ref vertices, ref index_count, ref indices,
                pentity.ParentNode._getDerivedPosition(),    // WorldPosition
                pentity.ParentNode._getDerivedOrientation(), // WorldOrientation
                pentity.ParentNode.GetScale());

            int ncf = -1; // new_closest_found

            // test for hitting individual triangles on the mesh
            for (int i = 0; i < (int)index_count; i += 3)
            {
                // check for a hit against this triangle
                Pair<bool, float> hit = Mogre.Math.Intersects(ray, vertices[indices[i]],
                    vertices[indices[i + 1]], vertices[indices[i + 2]], true, false);

                // if it was a hit check if its the closest
                if (hit.first)
                {
                    if ((closest_distance < 0.0f) ||
                        (hit.second < closest_distance))
                    {
                        // this is the closest so far, save it off
                        closest_distance = hit.second;
                        ncf = i;
                    }
                }
            }

            if (ncf > -1)
            {
                closest_result = ray.GetPoint(closest_distance);
                // if you don't need the normal, comment this out; you'll save some CPU cycles.
                Vector3 v1 = vertices[indices[ncf]] - vertices[indices[ncf + 1]];
                Vector3 v2 = vertices[indices[ncf + 2]] - vertices[indices[ncf + 1]];
                vNormal = v1.CrossProduct(v2);
            }

            // free the verticies and indicies memory
            vertices = null;
            indices = null;
        }
    }

    // if we found a new closest raycast for this object, update the
    // closest_result before moving on to the next object.
    if (closest_distance >= 0.0f)
    {
        result = new Vector3(closest_result.x, closest_result.y, closest_result.z);
        resNormal = vNormal / vNormal.Normalise();

        /*
        // this visualizes the 'result' position 
        if (!sceneMgr.HasSceneNode("marker"))
        {
            SceneNode node = sceneMgr.CreateSceneNode("marker");
            Entity ent = sceneMgr.CreateEntity("marker", "Cube.mesh");
            node.AttachObject(ent);
            node.Position = result;
            node.Scale(0.25f, 0.25f, 0.25f);
            sceneMgr.RootSceneNode.AddChild(node);
        }
        else
        {
            sceneMgr.GetSceneNode("marker").Position = result;
        }
        */

        // raycast success
        return true;
    }
    else
    {
        // raycast failed
        return false;
    }
} // RayCastFromPoint

GetMeshInformation

This code is a port from RetrieveVertexData.

There are two alternative versions of GetMeshInformation(). One takes into account the animation state of an entity and the other one solves compiling errors for 64bit using GCC.

// Get the mesh information for the given mesh.
// Code found in Wiki: www.ogre3d.org/wiki/index.php/RetrieveVertexData
public unsafe void GetMeshInformation(MeshPtr mesh,
    ref uint vertex_count,
    ref Vector3[] vertices,
    ref uint index_count,
    ref UInt64[] indices,
    Vector3 position,
    Quaternion orientation,
    Vector3 scale)
{
    bool added_shared = false;
    uint current_offset = 0;
    uint shared_offset = 0;
    uint next_offset = 0;
    uint index_offset = 0;

    vertex_count = index_count = 0;

    // Calculate how many vertices and indices we're going to need
    for (ushort i = 0; i < mesh.NumSubMeshes; ++i)
    {
        SubMesh submesh = mesh.GetSubMesh(i);

        // We only need to add the shared vertices once
        if (submesh.useSharedVertices)
        {
            if (!added_shared)
            {
                vertex_count += mesh.sharedVertexData.vertexCount;
                added_shared = true;
            }
        }
        else
        {
            vertex_count += submesh.vertexData.vertexCount;
        }

        // Add the indices
        index_count += submesh.indexData.indexCount;
    }

    // Allocate space for the vertices and indices
    vertices = new Vector3[vertex_count];
    indices = new UInt64[index_count];
    added_shared = false;

    // Run through the submeshes again, adding the data into the arrays
    for (ushort i = 0; i < mesh.NumSubMeshes; ++i)
    {
        SubMesh submesh = mesh.GetSubMesh(i);
        VertexData vertex_data = submesh.useSharedVertices ? mesh.sharedVertexData : submesh.vertexData;

        if (!submesh.useSharedVertices || (submesh.useSharedVertices && !added_shared))
        {
            if (submesh.useSharedVertices)
            {
                added_shared = true;
                shared_offset = current_offset;
            }

            VertexElement posElem =
                vertex_data.vertexDeclaration.FindElementBySemantic(VertexElementSemantic.VES_POSITION);
            HardwareVertexBufferSharedPtr vbuf =
                vertex_data.vertexBufferBinding.GetBuffer(posElem.Source);

            byte* vertex = (byte*)vbuf.Lock(HardwareBuffer.LockOptions.HBL_READ_ONLY);
            float* pReal;

            // There is _no_ baseVertexPointerToElement() which takes an Ogre::Real or a double
            //  as second argument. So make it float, to avoid trouble when Ogre::Real will
            //  be comiled/typedefed as double:
            //      Ogre::Real* pReal;
            for (int j = 0; j < vertex_data.vertexCount; ++j, vertex += vbuf.VertexSize)
            {
                posElem.BaseVertexPointerToElement(vertex, &pReal);
                Vector3 pt = new Vector3(pReal[0], pReal[1], pReal[2]);
                vertices[current_offset + j] = (orientation * (pt * scale)) + position;
            }
            // |!| Important: VertexBuffer Unlock() + Dispose() avoids memory corruption
            vbuf.Unlock();
            vbuf.Dispose();
            next_offset += vertex_data.vertexCount;
        }

        IndexData index_data = submesh.indexData;
        uint numTris = index_data.indexCount / 3;
        HardwareIndexBufferSharedPtr ibuf = index_data.indexBuffer;

        // UNPORTED line of C++ code (because ibuf.IsNull() doesn't exist in C#)
            // if( ibuf.isNull() ) continue
            // need to check if index buffer is valid (which will be not if the mesh doesn't have triangles like a pointcloud)
            
        bool use32bitindexes = (ibuf.Type == HardwareIndexBuffer.IndexType.IT_32BIT);

        uint* pLong = (uint*)ibuf.Lock(HardwareBuffer.LockOptions.HBL_READ_ONLY);
        ushort* pShort = (ushort*)pLong;
        uint offset = submesh.useSharedVertices ? shared_offset : current_offset;
        if (use32bitindexes)
        {
            for (int k = 0; k < index_data.indexCount; ++k)
            {
                indices[index_offset++] = (UInt64)pLong[k] + (UInt64)offset;
            }
        }
        else
        {
            for (int k = 0; k < index_data.indexCount; ++k)
            {
                indices[index_offset++] = (UInt64)pShort[k] + (UInt64)offset;
            }
        }
        // |!| Important: IndexBuffer Unlock() + Dispose() avoids memory corruption
        ibuf.Unlock();
        ibuf.Dispose();
        current_offset = next_offset;
    }

    // |!| Important: MeshPtr Dispose() avoids memory corruption
    mesh.Dispose(); // This dispose the MeshPtr, not the Mesh

} // GetMeshInformation


Alias: Raycasting_to_the_polygon_level_-_Mogre
Alias: Raycasting_to_the_polygon_level_%28Mogre%29

<HR>
Creative Commons Copyright -- Some rights reserved.


THE WORK (AS DEFINED BELOW) IS PROVIDED UNDER THE TERMS OF THIS CREATIVE COMMONS PUBLIC LICENSE ("CCPL" OR "LICENSE"). THE WORK IS PROTECTED BY COPYRIGHT AND/OR OTHER APPLICABLE LAW. ANY USE OF THE WORK OTHER THAN AS AUTHORIZED UNDER THIS LICENSE OR COPYRIGHT LAW IS PROHIBITED.

BY EXERCISING ANY RIGHTS TO THE WORK PROVIDED HERE, YOU ACCEPT AND AGREE TO BE BOUND BY THE TERMS OF THIS LICENSE. THE LICENSOR GRANTS YOU THE RIGHTS CONTAINED HERE IN CONSIDERATION OF YOUR ACCEPTANCE OF SUCH TERMS AND CONDITIONS.

1. Definitions

  • "Collective Work" means a work, such as a periodical issue, anthology or encyclopedia, in which the Work in its entirety in unmodified form, along with a number of other contributions, constituting separate and independent works in themselves, are assembled into a collective whole. A work that constitutes a Collective Work will not be considered a Derivative Work (as defined below) for the purposes of this License.
  • "Derivative Work" means a work based upon the Work or upon the Work and other pre-existing works, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, art reproduction, abridgment, condensation, or any other form in which the Work may be recast, transformed, or adapted, except that a work that constitutes a Collective Work will not be considered a Derivative Work for the purpose of this License. For the avoidance of doubt, where the Work is a musical composition or sound recording, the synchronization of the Work in timed-relation with a moving image ("synching") will be considered a Derivative Work for the purpose of this License.
  • "Licensor" means the individual or entity that offers the Work under the terms of this License.
  • "Original Author" means the individual or entity who created the Work.
  • "Work" means the copyrightable work of authorship offered under the terms of this License.
  • "You" means an individual or entity exercising rights under this License who has not previously violated the terms of this License with respect to the Work, or who has received express permission from the Licensor to exercise rights under this License despite a previous violation.
  • "License Elements" means the following high-level license attributes as selected by Licensor and indicated in the title of this License: Attribution, ShareAlike.

2. Fair Use Rights

Nothing in this license is intended to reduce, limit, or restrict any rights arising from fair use, first sale or other limitations on the exclusive rights of the copyright owner under copyright law or other applicable laws.

3. License Grant

Subject to the terms and conditions of this License, Licensor hereby grants You a worldwide, royalty-free, non-exclusive, perpetual (for the duration of the applicable copyright) license to exercise the rights in the Work as stated below:

  • to reproduce the Work, to incorporate the Work into one or more Collective Works, and to reproduce the Work as incorporated in the Collective Works;
  • to create and reproduce Derivative Works;
  • to distribute copies or phonorecords of, display publicly, perform publicly, and perform publicly by means of a digital audio transmission the Work including as incorporated in Collective Works;
  • to distribute copies or phonorecords of, display publicly, perform publicly, and perform publicly by means of a digital audio transmission Derivative Works.
  • For the avoidance of doubt, where the work is a musical composition:
    • Performance Royalties Under Blanket Licenses. Licensor waives the exclusive right to collect, whether individually or via a performance rights society (e.g. ASCAP, BMI, SESAC), royalties for the public performance or public digital performance (e.g. webcast) of the Work.
    • Mechanical Rights and Statutory Royalties. Licensor waives the exclusive right to collect, whether individually or via a music rights society or designated agent (e.g. Harry Fox Agency), royalties for any phonorecord You create from the Work ("cover version") and distribute, subject to the compulsory license created by 17 USC Section 115 of the US Copyright Act (or the equivalent in other jurisdictions).
    • Webcasting Rights and Statutory Royalties. For the avoidance of doubt, where the Work is a sound recording, Licensor waives the exclusive right to collect, whether individually or via a performance-rights society (e.g. SoundExchange), royalties for the public digital performance (e.g. webcast) of the Work, subject to the compulsory license created by 17 USC Section 114 of the US Copyright Act (or the equivalent in other jurisdictions).


The above rights may be exercised in all media and formats whether now known or hereafter devised. The above rights include the right to make such modifications as are technically necessary to exercise the rights in other media and formats. All rights not expressly granted by Licensor are hereby reserved.

4. Restrictions

The license granted in Section 3 above is expressly made subject to and limited by the following restrictions:

  • You may distribute, publicly display, publicly perform, or publicly digitally perform the Work only under the terms of this License, and You must include a copy of, or the Uniform Resource Identifier for, this License with every copy or phonorecord of the Work You distribute, publicly display, publicly perform, or publicly digitally perform. You may not offer or impose any terms on the Work that alter or restrict the terms of this License or the recipients' exercise of the rights granted hereunder. You may not sublicense the Work. You must keep intact all notices that refer to this License and to the disclaimer of warranties. You may not distribute, publicly display, publicly perform, or publicly digitally perform the Work with any technological measures that control access or use of the Work in a manner inconsistent with the terms of this License Agreement. The above applies to the Work as incorporated in a Collective Work, but this does not require the Collective Work apart from the Work itself to be made subject to the terms of this License. If You create a Collective Work, upon notice from any Licensor You must, to the extent practicable, remove from the Collective Work any credit as required by clause 4(c), as requested. If You create a Derivative Work, upon notice from any Licensor You must, to the extent practicable, remove from the Derivative Work any credit as required by clause 4(c), as requested.
  • You may distribute, publicly display, publicly perform, or publicly digitally perform a Derivative Work only under the terms of this License, a later version of this License with the same License Elements as this License, or a Creative Commons iCommons license that contains the same License Elements as this License (e.g. Attribution-ShareAlike 2.5 Japan). You must include a copy of, or the Uniform Resource Identifier for, this License or other license specified in the previous sentence with every copy or phonorecord of each Derivative Work You distribute, publicly display, publicly perform, or publicly digitally perform. You may not offer or impose any terms on the Derivative Works that alter or restrict the terms of this License or the recipients' exercise of the rights granted hereunder, and You must keep intact all notices that refer to this License and to the disclaimer of warranties. You may not distribute, publicly display, publicly perform, or publicly digitally perform the Derivative Work with any technological measures that control access or use of the Work in a manner inconsistent with the terms of this License Agreement. The above applies to the Derivative Work as incorporated in a Collective Work, but this does not require the Collective Work apart from the Derivative Work itself to be made subject to the terms of this License.
  • If you distribute, publicly display, publicly perform, or publicly digitally perform the Work or any Derivative Works or Collective Works, You must keep intact all copyright notices for the Work and provide, reasonable to the medium or means You are utilizing: (i) the name of the Original Author (or pseudonym, if applicable) if supplied, and/or (ii) if the Original Author and/or Licensor designate another party or parties (e.g. a sponsor institute, publishing entity, journal) for attribution in Licensor's copyright notice, terms of service or by other reasonable means, the name of such party or parties; the title of the Work if supplied; to the extent reasonably practicable, the Uniform Resource Identifier, if any, that Licensor specifies to be associated with the Work, unless such URI does not refer to the copyright notice or licensing information for the Work; and in the case of a Derivative Work, a credit identifying the use of the Work in the Derivative Work (e.g., "French translation of the Work by Original Author," or "Screenplay based on original Work by Original Author"). Such credit may be implemented in any reasonable manner; provided, however, that in the case of a Derivative Work or Collective Work, at a minimum such credit will appear where any other comparable authorship credit appears and in a manner at least as prominent as such other comparable authorship credit.

5. Representations, Warranties and Disclaimer

UNLESS OTHERWISE AGREED TO BY THE PARTIES IN WRITING, LICENSOR OFFERS THE WORK AS-IS AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE MATERIALS, EXPRESS, IMPLIED, STATUTORY OR OTHERWISE, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTIBILITY, FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT, OR THE ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OF ABSENCE OF ERRORS, WHETHER OR NOT DISCOVERABLE. SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OF IMPLIED WARRANTIES, SO SUCH EXCLUSION MAY NOT APPLY TO YOU.

6. Limitation on Liability.

EXCEPT TO THE EXTENT REQUIRED BY APPLICABLE LAW, IN NO EVENT WILL LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY FOR ANY SPECIAL, INCIDENTAL, CONSEQUENTIAL, PUNITIVE OR EXEMPLARY DAMAGES ARISING OUT OF THIS LICENSE OR THE USE OF THE WORK, EVEN IF LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

7. Termination

  • This License and the rights granted hereunder will terminate automatically upon any breach by You of the terms of this License. Individuals or entities who have received Derivative Works or Collective Works from You under this License, however, will not have their licenses terminated provided such individuals or entities remain in full compliance with those licenses. Sections 1, 2, 5, 6, 7, and 8 will survive any termination of this License.
  • Subject to the above terms and conditions, the license granted here is perpetual (for the duration of the applicable copyright in the Work). Notwithstanding the above, Licensor reserves the right to release the Work under different license terms or to stop distributing the Work at any time; provided, however that any such election will not serve to withdraw this License (or any other license that has been, or is required to be, granted under the terms of this License), and this License will continue in full force and effect unless terminated as stated above.

8. Miscellaneous

  • Each time You distribute or publicly digitally perform the Work or a Collective Work, the Licensor offers to the recipient a license to the Work on the same terms and conditions as the license granted to You under this License.
  • Each time You distribute or publicly digitally perform a Derivative Work, Licensor offers to the recipient a license to the original Work on the same terms and conditions as the license granted to You under this License.
  • If any provision of this License is invalid or unenforceable under applicable law, it shall not affect the validity or enforceability of the remainder of the terms of this License, and without further action by the parties to this agreement, such provision shall be reformed to the minimum extent necessary to make such provision valid and enforceable.
  • No term or provision of this License shall be deemed waived and no breach consented to unless such waiver or consent shall be in writing and signed by the party to be charged with such waiver or consent.
  • This License constitutes the entire agreement between the parties with respect to the Work licensed here. There are no understandings, agreements or representations with respect to the Work not specified here. Licensor shall not be bound by any additional provisions that may appear in any communication from You. This License may not be modified without the mutual written agreement of the Licensor and You.