wang min - Page 15 - Developer IT

First-Time GLSL Shadow Mapping Problems

- by Locke

I'm working on building out a 2.5D engine and having massive problems getting my shadows working. I'm at a point where I'm VERY close. So, let's see a picture to see what I have: As you can see above, the image has lighting -- but the shadow map is displaying incorrectly. The shadow map is shown in the bottom left hand side of the screen as a normal 2D texture, so we can see what it looks like at any given time. If you notice, it appears that the shadows are generating backwards in the wrong direction -- I think. But the problem is a little more deep -- I'm just plotting the shadow onto the screen, which I know is wrong -- I'm ignoring the actual test to see if we NEED to show a shadow. The incoming parameters all appear to be correct -- so there has to be something wrong with my shader code somewhere. Here's what my code looks like: VERTEX: uniform mat4 LightModelViewProjectionMatrix; varying vec3 Normal; // The eye-space normal of the current vertex. varying vec4 LightCoordinate; // The texture coordinate of the light of the current vertex. varying vec3 LightDirection; // The eye-space direction of the light. void main() { Normal = normalize(gl_NormalMatrix * gl_Normal); LightDirection = normalize(gl_NormalMatrix * gl_LightSource[0].position.xyz); LightCoordinate = LightModelViewProjectionMatrix * gl_Vertex; LightCoordinate.xy = ( LightCoordinate.xy * 0.5 ) + 0.5; gl_Position = ftransform(); gl_TexCoord[0] = gl_MultiTexCoord0; } FRAGMENT: uniform sampler2D DiffuseMap; uniform sampler2D ShadowMap; varying vec3 Normal; // The eye-space normal of the current vertex. varying vec4 LightCoordinate; // The texture coordinate of the light of the current vertex. varying vec3 LightDirection; // The eye-space direction of the light. void main() { vec4 Texel = texture2D(DiffuseMap, vec2(gl_TexCoord[0])); // Directional lighting //Build ambient lighting vec4 AmbientElement = gl_LightSource[0].ambient; //Build diffuse lighting float Lambert = max(dot(Normal, LightDirection), 0.0); //max(abs(dot(Normal, LightDirection)), 0.0); vec4 DiffuseElement = ( gl_LightSource[0].diffuse * Lambert ); vec4 LightingColor = ( DiffuseElement + AmbientElement ); LightingColor.r = min(LightingColor.r, 1.0); LightingColor.g = min(LightingColor.g, 1.0); LightingColor.b = min(LightingColor.b, 1.0); LightingColor.a = min(LightingColor.a, 1.0); LightingColor *= Texel; //Everything up to this point is PERFECT // Shadow mapping // ------------------------------ vec4 ShadowCoordinate = LightCoordinate / LightCoordinate.w; float DistanceFromLight = texture2D( ShadowMap, ShadowCoordinate.st ).z; float DepthBias = 0.001; float ShadowFactor = 1.0; if( LightCoordinate.w > 0.0 ) { ShadowFactor = DistanceFromLight < ( ShadowCoordinate.z + DepthBias ) ? 0.5 : 1.0; } LightingColor.rgb *= ShadowFactor; //gl_FragColor = LightingColor; //Yes, I know this is wrong, but the line above (gl_FragColor = LightingColor;) produces the wrong effect gl_FragColor = LightingColor * texture2D( ShadowMap, ShadowCoordinate.st ); } I wanted to make sure the coordinates were correct for the shadow map -- so that's why you see it applied to the image as it is below. But the depth for each point seems to be wrong -- the shadows SHOULD be opposite (look at how the image is -- the shaded areas from normal lighting are facing the opposite direction of the shadows). Maybe my matrices are bad or something going in? They're isolated and appear to be correct -- nothing else is going in unusual. When I view from the light's view and get the MVP matrices for it, they're correct. EDIT: Added an image so you can see what happens when I do the correct command at the end of the GLSL: That's the image when the last line is just glFragColor = LightingColor; Maybe someone has some idea of what I screwed up?

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