From de7bca7ef8b006acd0b5c8ca4f41093c77f5ff4a Mon Sep 17 00:00:00 2001
From: Philip Rideout <philiprideout@gmail.com>
Date: Wed, 28 Sep 2022 17:02:28 -0700
Subject: [PATCH] gltfio: fix occlusion strength

Fixes #6106
---
 RELEASE_NOTES.md                          | 1 +
 libs/gltfio/materials/base.mat.in         | 4 ++--
 libs/gltfio/materials/sheen.mat.in        | 4 ++--
 libs/gltfio/materials/transmission.mat.in | 4 ++--
 libs/gltfio/materials/volume.mat.in       | 4 ++--
 libs/gltfio/src/JitShaderProvider.cpp     | 4 ++--
 6 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 6c6b19f729..cd53726efe 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -8,6 +8,7 @@ A new header is inserted each time a *tag* is created.
 - engine: LiSPSM is now a user settable option
 - Java: Fix TransformManager.getChildren()
 - Metal: newer devices are no longer limited to 16 samplers per Material.
+- gltfio: fix interpretation of occlusion strength
 
 ## v1.27.2
 
diff --git a/libs/gltfio/materials/base.mat.in b/libs/gltfio/materials/base.mat.in
index bd0fb37b2f..da62ce9f8b 100644
--- a/libs/gltfio/materials/base.mat.in
+++ b/libs/gltfio/materials/base.mat.in
@@ -163,8 +163,8 @@ fragment {
             if (materialParams.aoIndex > -1) {
                 highp float2 uv = uvs[materialParams.aoIndex];
                 uv = (vec3(uv, 1.0) * materialParams.occlusionUvMatrix).xy;
-                material.ambientOcclusion = texture(materialParams_occlusionMap, uv).r *
-                        materialParams.aoStrength;
+                float occlusion = texture(materialParams_occlusionMap, uv).r;
+                material.ambientOcclusion = 1.0 + materialParams.aoStrength * (occlusion - 1.0);
             }
             if (materialParams.emissiveIndex > -1) {
                 highp float2 uv = uvs[materialParams.emissiveIndex];
diff --git a/libs/gltfio/materials/sheen.mat.in b/libs/gltfio/materials/sheen.mat.in
index f579f12ad8..b8682ca34f 100644
--- a/libs/gltfio/materials/sheen.mat.in
+++ b/libs/gltfio/materials/sheen.mat.in
@@ -127,8 +127,8 @@ fragment {
         if (materialParams.aoIndex > -1) {
             highp float2 uv = uvs[materialParams.aoIndex];
             uv = (vec3(uv, 1.0) * materialParams.occlusionUvMatrix).xy;
-            material.ambientOcclusion = texture(materialParams_occlusionMap, uv).r *
-                    materialParams.aoStrength;
+            float occlusion = texture(materialParams_occlusionMap, uv).r;
+            material.ambientOcclusion = 1.0 + materialParams.aoStrength * (occlusion - 1.0);
         }
         if (materialParams.emissiveIndex > -1) {
             highp float2 uv = uvs[materialParams.emissiveIndex];
diff --git a/libs/gltfio/materials/transmission.mat.in b/libs/gltfio/materials/transmission.mat.in
index d0b518631a..3b1cd2283f 100644
--- a/libs/gltfio/materials/transmission.mat.in
+++ b/libs/gltfio/materials/transmission.mat.in
@@ -117,8 +117,8 @@ fragment {
         if (materialParams.aoIndex > -1) {
             highp float2 uv = uvs[materialParams.aoIndex];
             uv = (vec3(uv, 1.0) * materialParams.occlusionUvMatrix).xy;
-            material.ambientOcclusion = texture(materialParams_occlusionMap, uv).r *
-                    materialParams.aoStrength;
+            float occlusion = texture(materialParams_occlusionMap, uv).r;
+            material.ambientOcclusion = 1.0 + materialParams.aoStrength * (occlusion - 1.0);
         }
         if (materialParams.emissiveIndex > -1) {
             highp float2 uv = uvs[materialParams.emissiveIndex];
diff --git a/libs/gltfio/materials/volume.mat.in b/libs/gltfio/materials/volume.mat.in
index 432ea88d54..364da89627 100644
--- a/libs/gltfio/materials/volume.mat.in
+++ b/libs/gltfio/materials/volume.mat.in
@@ -133,8 +133,8 @@ fragment {
         if (materialParams.aoIndex > -1) {
             highp float2 uv = uvs[materialParams.aoIndex];
             uv = (vec3(uv, 1.0) * materialParams.occlusionUvMatrix).xy;
-            material.ambientOcclusion = texture(materialParams_occlusionMap, uv).r *
-                    materialParams.aoStrength;
+            float occlusion = texture(materialParams_occlusionMap, uv).r;
+            material.ambientOcclusion = 1.0 + materialParams.aoStrength * (occlusion - 1.0);
         }
         if (materialParams.emissiveIndex > -1) {
             highp float2 uv = uvs[materialParams.emissiveIndex];
diff --git a/libs/gltfio/src/JitShaderProvider.cpp b/libs/gltfio/src/JitShaderProvider.cpp
index 5fa1100304..5423643473 100644
--- a/libs/gltfio/src/JitShaderProvider.cpp
+++ b/libs/gltfio/src/JitShaderProvider.cpp
@@ -194,8 +194,8 @@ std::string shaderFromKey(const MaterialKey& config) {
                 shader += "aoUV = (vec3(aoUV, 1.0) * materialParams.occlusionUvMatrix).xy;\n";
             }
             shader += R"SHADER(
-                material.ambientOcclusion = texture(materialParams_occlusionMap, aoUV).r *
-                        materialParams.aoStrength;
+                float occlusion = texture(materialParams_occlusionMap, aoUV).r;
+                material.ambientOcclusion = 1.0 + materialParams.aoStrength * (occlusion - 1.0);
             )SHADER";
         }
         if (config.hasEmissiveTexture) {