today I was trying to unproject my mouse position to see where it is in world space.
Here it is the unproject function:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | //project is the same exact matrix passed to opengl
Vec3 Unproject( Renderer* renderer, Camera* camera, matrix4x4 project, matrix4x4 backward, Vec2 screenP, r32 distanceFromCameraZ)
{
//compute ndc X and Y based on screen coordinates
Vec2 screenCenter = 0.5f * renderer->screenDim;
r32 ndcX = (screenP.x - screenCenter.x) * (2.0f / renderer->screenDim.x);
r32 ndcY = (screenP.y - screenCenter.y) * (2.0f / renderer->screenDim.y);
//let's see what's the clipZ of the targetZ
Vec4 probeZ = V4( camera->Position -worldDistanceFromCameraZ * camera->ZAxis, 1.0f );
//for debugging, let's force the worldZ of the probe to be on the ground plane, so that our points will always be on the ground plane
probeZ.z = 0;
probeZ = project * probeZ;
r32 clipZ =probeZ.z;
//"backward" perspective divide to obtain the clip coordinates
Vec4 clip = clipZ * V4(ndcX, ndcY, 1.0f, 1.0f);
//"backward" projection to obtain world coordinates
Vec3 world = (backward * clip).xyz;
return world;
}
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It seems to work fine when the camera is perfectly aligned with the world Z Axis (0, 0, 1): (you can see the red rectangle perfectly fits the screen)
https://ibb.co/iejA9z
but as soon as I start rotating the camera it doesn't work anymore, as it seems it is still using the straight up camera.
https://ibb.co/msPXNK
Assuming the problem is not in the camera matrixes (checked multiple times both the forward and back matrixes), I think the problem should be _somewhere_ in this function, but I really can't see it.
Can you guys give me a little help with this?
Thank you,
Leonardo