Convenient way to determine exact point under mouse

3D
4

It is possible. Albeit we would employ some assumptions/epsilons but yes, you can do this. It means you need to query for collision repeatedly – because the collision routines consider the geometry (ignoring whether the texture at them is transparent or not). So you need to make a collision query, then look if you hit a transparent pixel on a texture, and if yes – make a new collision query from a new origin.

To do this:

  • You need to use a more general method MyViewport.CameraRayCollision(RayOrigin, RayDirection) . It returns TRayCollision, just like MouseRayHit (so it can be processed in the same way as above to detect the particular point). It takes as input ray position and direction.

  • Use it in a loop.

    • The initial RayOrigin, RayDirection can come from the mouse position – use MyViewport.PositionToRay.

    • Make a call to MyViewport.CameraRayCollision(RayOrigin, RayDirection). If something was hit, but the texture pixel at the hit point is transparent, make another call to MyViewport.CameraRayCollision(NewRayOrigin, RayDirection). The NewRayOrigin should be “HitPosition + RayDirection.AdjustToLength(SomeEpsilon)”.

    • The remaining task is to query the texture pixel at the hit point. To do this, note that TRayCollisionNode has a reference to Triangle . Use TTriangle.ITexCoord to get texture coordinate at the hit point, and finally use this texture coordinate to query the texture image (e.g. from TImageTextureNode.TextureImage). If the queried pixel has alpha < 0.5, you can consider it transparent, and thus repeat the call.