I have a simple deferred rendering setup and I'm trying to get depth map shadows to work. I know that I have a simple error in my code because I can see the shadows working, but they seem to move and lose resolution when I move my camera. This is not a Shadow Acne Problem. The shadow is shifted entirely. I have also seen most of the similar questions here, but none solve my problem.
In my final shader, I have a texture for world space positions of pixels, and the depth map rendered from the light source, as well as the light source's model-view-projection matrix. The steps I take are:
- Get worldspace position of pixel from pre-rendered pass.
Multiply worldspace position with the light source's model-view-projection matrix. I am using orthogonal projection (a directional light).
glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(-0.0025, 0.0025, -0.0025, 0.0025, -0.1, 0.1); glGetFloatv(GL_PROJECTION_MATRIX,m_lightViewProjectionMatrix);
I place the directional light at a fixed distance around my hero. Here is how I get my light's modelview matrix:
CSRTTransform lightTrans = CSRTTransform();
CVector camOffset = CVector(m_vPlanet[0].m_vLightPos);
camOffset.Normalize();
camOffset *= 0.007;
camOffset += hero.GetLocation();
CVector LPN = m_vLightPos*(-1); LPN.Normalize();
CQuaternion lRot;
lRot = CQuaternion( CVector(0,1,0), asin(LPN | CVector(-1,0,0) ) );
lightTrans.m_qRotate = lRot;
lightTrans.m_vTranslate = camOffset;
m_worldToLightViewMatrix = lightTrans.BuildViewMatrix();
And the final light mvp matrix is:
CMatrix4 lightMVPMatrix = m_lightViewProjectionMatrix * m_worldToLightViewMatrix;
m_shHDR.SetUniformMatrix("LightMVPMatrix", lightMVPMatrix);
For now I am only rendering the shadow casters in my shadow pass. As you can see, the shadow pass seems fine, my hero is centered in the frame and rotated correctly. It is worth noting that these two matrices are passed to the vertex shader of the hero so it seems like they are correct because the hero is rendered correctly in the shadow pass (shown here with more contrast for visibility).
And finally, in my deferred shader I do:
vec4 projectedWorldPos = LightMVPMatrix * vec4(worldPos,1.0);
vec3 projCoords = projectedWorldPos.xyz;//projectedWorldPos.w;
projCoords.xyz = (projCoords.xyz * 0.5) + 0.5;
float calc_depth = projCoords.z;
float tD = texture2DRect(shadowPass,vec2(projCoords.x*1280.0,projCoords.y*720.0)).r ;
return ( calc_depth < tD ) ;
I have the /w division commented out because I'm using orthogonal projection. Having it produces the same result anyways.
In certain positions for my hero (close to initial position) (1), the shadow looks fine. But as soon as I move the hero, the shadow moves incorrectly (2), and the further away I move, the shadow starts to lose resolution (3).
It is worth noting all my textures and passes are the same size (1280x720). I'm using an NVidia graphics card. The problem seems to be matrix related, but as mentioned, the shadow pass renders OK so I'm not sure what's going on...
