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Approximate specularity / glossiness in metallicRoughness materials

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Before, models (of traditional lighting models) with specularity/glossiness would be completely flat when exported to metallicRoughness. These changes approximate glossiness (as an inverse of roughness, with specular intensity as a multiplier) both reading from gltf2 and writing to gltf2.
This commit is contained in:
Daniel Hritzkiv
2017-10-19 12:30:32 -04:00
parent a898c1f2d1
commit 89358458f0
2 changed files with 39 additions and 2 deletions
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34
code/glTF2Exporter.cpp
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@@ -434,7 +434,29 @@ void glTF2Exporter::ExportMaterials()
m->pbrMetallicRoughness.metallicFactor = 0;
}
mat->Get(AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR, m->pbrMetallicRoughness.roughnessFactor);
// get roughness if source is gltf2 file
if (mat->Get(AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR, m->pbrMetallicRoughness.roughnessFactor) != AI_SUCCESS) {
// otherwise, try to derive and convert from specular + shininess values
aiColor4D specularColor;
ai_real shininess;
if (
mat->Get(AI_MATKEY_COLOR_SPECULAR, specularColor) == AI_SUCCESS &&
mat->Get(AI_MATKEY_SHININESS, shininess) == AI_SUCCESS
) {
// convert specular color to luminance
float specularIntensity = specularColor[0] * 0.2125 + specularColor[1] * 0.7154 + specularColor[2] * 0.0721;
float roughnessFactor = 1 - std::sqrt(shininess / 1000);
roughnessFactor = std::powf(roughnessFactor, 2);
roughnessFactor = std::min(std::max(roughnessFactor, 0.0f), 1.0f);
// low specular intensity values should produce a rough material even if shininess is high.
roughnessFactor = 1 - (roughnessFactor * specularIntensity);
m->pbrMetallicRoughness.roughnessFactor = roughnessFactor;
}
}
GetMatTex(mat, m->normalTexture, aiTextureType_NORMALS);
GetMatTex(mat, m->occlusionTexture, aiTextureType_LIGHTMAP);
@@ -470,9 +492,17 @@ void glTF2Exporter::ExportMaterials()
PbrSpecularGlossiness pbrSG;
mat->Get(AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR, pbrSG.glossinessFactor);
GetMatColor(mat, pbrSG.diffuseFactor, AI_MATKEY_COLOR_DIFFUSE);
GetMatColor(mat, pbrSG.specularFactor, AI_MATKEY_COLOR_SPECULAR);
if (mat->Get(AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) != AI_SUCCESS) {
float shininess;
if (mat->Get(AI_MATKEY_SHININESS, shininess)) {
pbrSG.glossinessFactor = shininess / 1000;
}
}
GetMatTex(mat, pbrSG.diffuseTexture, aiTextureType_DIFFUSE);
GetMatTex(mat, pbrSG.specularGlossinessTexture, aiTextureType_SPECULAR);