cg shadow mapping
Author
hi all,
I'm trying going through nvidia's The Cg Tutorial in and am having some difficulties with recreating the shadow mapping example in opengl.
First, I'm render the scene from the light's perspective into an FBO which is used to store the depth buffer. (fovy=60, aspect=512/512, znear=0.1, zfar = 10.0)
Next, I render the scene again from the point of view of the camera and use the texture matrix to get the projective texture coords to be used in the shader.
My scene is a sphere floating about a plane with the light above the sphere.
All this seems to work but I get strange artifacts on the sphere.
Any help would be greatly appreciate, this is driving me mad!!!
Does it not happen in DirectX?
What format are you using for the depth map?
Are you using a polygon offset when rendering to the depth map?
What format are you using for the depth map?
Are you using a polygon offset when rendering to the depth map?
Author
I haven't tried it in direct x (still only know opengl)
This is how I set up the depth map texture:
glGenTextures (1, &depthTex);
glBindTexture (GL_TEXTURE_2D, depthTex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE,GL_COMPARE_R_TO_TEXTURE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, width, height, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
As for the polygon offset I use:
glEnable(GL_POLYGON_OFFSET_FILL);
glPolygonOffset(3, 3);
Could it be the values I'm supplying to this function?
My light is at (0,2,0) and the sphere has a radius of 0.3 with center 0.5 units above the ground plane.
This is how I set up the depth map texture:
glGenTextures (1, &depthTex);
glBindTexture (GL_TEXTURE_2D, depthTex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE,GL_COMPARE_R_TO_TEXTURE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT24, width, height, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
As for the polygon offset I use:
glEnable(GL_POLYGON_OFFSET_FILL);
glPolygonOffset(3, 3);
Could it be the values I'm supplying to this function?
My light is at (0,2,0) and the sphere has a radius of 0.3 with center 0.5 units above the ground plane.
My guess is that it's just a standard shadow map artifact. Surfaces normals that are at a high angle with respect to the light end up mapping to very few texels in the depth map. A simple fix is to only perform the shadow test if a pixel's normal * light direction is above some threshold. This would be done in the pixel shader of course.
I assume you're doing a PCF?
Also, could you zoom into the shadow edge a bit?
I assume you're doing a PCF?
Also, could you zoom into the shadow edge a bit?
Author
I'm just using standard shadow mapping, nothing fancy:
void C5E2f_ShadowMap( float4 texCoord: TEXCOORD0, float3 position : TEXCOORD1, float3 normal : TEXCOORD2, out float4 color : COLOR, uniform float3 lightPosition, uniform float3 eyePosition, uniform sampler2D shadowmap){ float3 P = position.xyz; float3 N = normalize(normal); float3 L = normalize(lightPosition - P); float diffuse = max(dot(N, L), 0.0); /* visibility is set to 0 when in shadow and 1 when not in shadow */ float4 shadowCoeff = tex2Dproj(shadowmap, texCoord); color.xyz = float3(0.8 * diffuse * shadowCoeff + 0.1); color.w = 1.0; }
it looks like the light source producing the shading on the ball doesnt match the light source casting the shadow, that should fix it up a bit
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