Initial refraction approximation in GLSL #918
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This changelist introduces a rough approximation of refraction in GLSL, allowing transmissive materials such as glass to respond visually to changes in specular_IOR, specular_roughness, and transmission_color. Because this initial approximation is limited to a single render pass, only the environment radiance map is currently visible in refractions, and opaque objects behind transmissive surfaces are not yet visible.
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The following renders are from MaterialXView, showing the proposed refraction approximation in the context of transmissive Standard Surface materials: Standard Surface Glass: Standard Surface Glass Tinted: |
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Thanks to @mjyip-lucasfilm for her significant contributions to this work! |
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Reference renders in GLSL and OSL: |
| @@ -34,7 +34,7 @@ vec3 mx_environment_radiance(vec3 N, vec3 V, vec3 X, vec2 alpha, int distributio | |||
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| // Compute the half vector and incoming light direction. | |||
| vec3 H = mx_ggx_importance_sample_NDF(Xi, alpha); | |||
| vec3 L = -reflect(V, H); | |||
| vec3 L = fd.refraction ? mx_refraction_solid_sphere(-V, H, fd.ior.x) : -reflect(V, H); | |||
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Just a note for the future that we need to split this switch in two later to support thin-walled materials. We then need to have separate control of transmission and refraction on/off, since we can have transmission without refraction in that case, but still transmission with a roughness.
| // glossy environment map refraction, ignoring any scene geometry that | ||
| // might be visible through the surface. | ||
| fd.refraction = true; | ||
| vec3 Li = $refractionEnv ? mx_environment_radiance(N, V, X, safeAlpha, distribution, fd) : $refractionColor; |
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Out of curiosity why is there an option to replace the refracted environment with a uniform color? We don't have a corresponding control for environment reflections. Or is this just for debugging for now?
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That option was primarily added for our GLSL/OSL reference renders, since OSL testrender refracts the constant-color background instead of the distant environment.
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Aha! Maybe we should fix this so the environment is visible in both reflection and transmission, for both GLSL and OSL test suite rendering. Lets do that in a separate PR though.
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Looks great @jstone-lucasfilm. I only had some minor comments above.
This changelist introduces a rough approximation of refraction in GLSL, allowing transmissive materials such as glass to respond visually to changes in specular_IOR, specular_roughness, and transmission_color. Because this initial approximation is limited to a single render pass, only the environment radiance map is currently visible in refractions, and opaque objects behind transmissive surfaces are not yet visible.
This changelist introduces a rough approximation of refraction in GLSL, allowing transmissive materials such as glass to respond visually to changes in specular_IOR, specular_roughness, and transmission_color.
Because this initial approximation is limited to a single render pass, only the environment radiance map is currently visible in refractions, and opaque objects behind transmissive surfaces are not yet visible.