[need Help] Collision with texture

Hey jme Com!
I started with the Irrlicht engine and now I am happy that I switched to JME.
My First Project is something like a paint game, atm I try to create a blank texture who is then editable by “shooting (aiming)” at it.
So I seperated a plane into 16 pieces (I know coordinates in 2D) and I cast a Ray from Player to this Plane.
But how can I now cast this 3D Point into the 2D Format from the texture ?
Would be awesome if you can give me some Hints :slight_smile:
Thx Sero

I’m now trying to solve exactly same problem (mentioned here http://hub.jmonkeyengine.org/forum/topic/javafx-embedded-in-jme3/page/11/#post-293190 ). Basically, convert collision point into barycentric coordinates for collission triangle and use them to interpolate texture coordinates for same triangle. I should have some code available in few hours.

Cut, pasted, and cleaned up a bit from code I have to do similar for passing events through to a UI based on clicks on an object:

Geometry geom = cr.getGeometry();
Mesh mesh = geom.getMesh();
IndexBuffer ib = mesh.getIndexBuffer();

    // Get the infor for the triangle we are interested in
    int triIndex = cr.getTriangleIndex();
    int[] indexes = new int[3];
    indexes[0] = ib.get(triIndex * 3);
    indexes[1] = ib.get(triIndex * 3 + 1);
    indexes[2] = ib.get(triIndex * 3 + 2);
    Vector3f[] verts = new Vector3f[3]; 
    Vector2f[] texes = new Vector2f[3];
    FloatBuffer pb = mesh.getFloatBuffer(VertexBuffer.Type.Position); 
    FloatBuffer tb = mesh.getFloatBuffer(VertexBuffer.Type.TexCoord); 
    // The vertexes and UVs for the three triangle corners 
    for( int i = 0; i < 3; i++ ) {
        int j = indexes[i];
        verts[i] = new Vector3f(pb.get(j*3), pb.get(j*3+1), pb.get(j*3+2));
        texes[i] = new Vector2f(tb.get(j*2), tb.get(j*2+1));                
    // Find the point in mesh space
    Vector3f p = cr.getContactPoint();
    p = geom.worldToLocal(p, null);
    // Now use this:             
    // http://www.blackpawn.com/texts/pointinpoly/default.html
    // ...to get the barycentric coordinates of the triangle
    // this I think goes all the way:
    // http://www.gamedev.net/topic/569449-texture-coordinates-at-a-point-on-triangle/
    Vector3f v0 = verts[2].subtract(verts[0]);
    Vector3f v1 = verts[1].subtract(verts[0]);
    Vector3f v2 = p.subtract(verts[0]);
    float dot00 = v0.dot(v0);
    float dot01 = v0.dot(v1);
    float dot02 = v0.dot(v2);
    float dot11 = v1.dot(v1);
    float dot12 = v1.dot(v2);

    float invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
    float u = (dot11 * dot02 - dot01 * dot12) * invDenom;
    float v = (dot00 * dot12 - dot01 * dot02) * invDenom;

    // Use the barycentric uv to interpolate a new real 'texture coordinate'
    Vector2f t2 = texes[1].subtract(texes[0]);
    Vector2f t1 = texes[2].subtract(texes[0]);
    Vector2f newUV = texes[0].add(t1.mult(u)).add(t2.mult(v));


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My code at the moment for getting hit tex coordinates is (assuming:
tmp being temporary variables
p0,p1,p2 - triangle vertex positions in model space
t0,t1,t2 - corresponding texture coordinates for vertices
cp - contact point from collision results
geom - geometry in question


Vector3f vn = p2.subtract(p1, tmp.vect4).crossLocal(p1.subtract(p0,tmp.vect5));
float A = vn.length();
Vector3f n = tmp.vect6.set(vn).divideLocal(A);
float u = FastMath.abs((p2.subtract(p1,tmp.vect7).crossLocal(cp.subtract(p1,tmp.vect8))).dot(n) / A);
float v = FastMath.abs((p0.subtract(p2,tmp.vect7).crossLocal(cp.subtract(p2,tmp.vect8))).dot(n) / A);
float w = 1 - u - v;
float s = t0.x * u + t1.x * v + t2.x * w;
float t = t0.y * u + t1.y * v + t2.y * w;

I don’t like abs around u and v, but I think it has something to do with computed normal pointing into wrong direction. Probably can be fixed by switching order of vectors, but I don’t feel too confident playing with this formula.