How do you double-check normal map output? (screenshot)

Caleb Gingles · 2011-09-01T17:10:25

I'm currently trying to learn how to do deferred shading, and in the process I'm trying to make sure my normals are being rendered properly to my FBO texture. I'm using gDEbugger to examine the contents of the FBO textures, and the normal texture is a GL_RGBA16F. The problem is, I don't know if I am properly transforming my normal map to view space in preparation for deferred lighting. The transformed MRT image appears correct, in terms of the positions of the color variations, but the overall coloring of the result is different from what I've seen in tutorials and other examples. In the examples I've seen, the resulting output remains as vibrant as the original normal map image. That isn't the case for me, but I'm not sure what I'm doing wrong. Here is a comparison image. The left one is a plain render of the normal map texture to the cube. The one on the right has the normal map transformed into view space. Gradient positions look right in the transformed image, but the overall coloring seems weird. I don't know how well gDEbugger visualizes RGBA16F textures, or how to check what the actual values are (all gDEbugger shows me are 0-255 color channel values). Here are the (minimal) shaders I'm using currently, if it helps: Vertex shader: #version 150 uniform mat4 worldproj; uniform mat4 world; in vec4 position; in vec3 normal; in vec3 tangent; in vec3 bitangent; in vec2 texture; out vec3 v2f_normal; out vec3 v2f_tangent; out vec3 v2f_bitangent; out vec2 v2f_texture; void main() { gl_Position = worldproj * position; mat3 worldrot = mat3(world); v2f_normal = worldrot * normal; v2f_tangent = worldrot * tangent; v2f_bitangent = worldrot * bitangent; v2f_texture = texture; } Fragment shader: #version 150 in vec3 v2f_normal; in vec3 v2f_tangent; in vec3 v2f_bitangent; in vec2 v2f_texture; out vec4 outColor; out vec4 outNormal; out vec4 outPosition; uniform sampler2D texture0; uniform sampler2D texture1; void main() { outColor = texture2D( texture0, v2f_texture ); outColor.a = 1; vec3 normal = vec3( texture2D( texture1, v2f_texture ) ) - 0.5; mat3 t; t[0] = v2f_tangent; t[1] = -v2f_bitangent; t[2] = v2f_normal; normal = normalize( normal * t ); outNormal = vec4(normal * 0.5 + 0.5, 1.0); outPosition = texture2D( texture1, v2f_texture ); }

Graphics and GPU Programming Programming

Started by Nairou August 30, 2011 05:56 AM

9 comments, last by Nairou 12 years, 7 months ago

Nairou

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Author

September 01, 2011 05:10 PM

The orientation of the z component of the normals will depend on the handedness of the coordinate system you are usng; looks like you're view-space is left-handed, since +x goes to the right, +y goes up and +z goes into the screen (hence you see very little blue).

As for the colours not "blending as well" - it's because you're not remapping into [0,1] to visualize the normals.

Ahh... That makes perfect sense now. Thank you!

How do you double-check normal map output? (screenshot)

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How do you double-check normal map output? (screenshot)

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