Fix shadowed models despite recievesShadows=false6.7

Even though Model::recievesShadows is set to false, sometimes the model
is rendered as completely shadowed. In the shadow mapping shader, the
light matrix is all zeroes when recievesShadows is false. As a
consequence of this we get a NaN value in 'smpCoord' and a division by
zero. We can mitigate this by simply checking if the 'shadowFactor' is
close to zero and just skip calling the shadow mapping function.

Pick-to: 6.5
Change-Id: I9ee6fe0219a7c4ca4b20c9cd24eaf9044d3d5fe6
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
(cherry picked from commit c17345351f4ebc9a45d0eb1e3f70b0012297a0e8)
Reviewed-by: Jonas Karlsson <jonas.karlsson@qt.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/runtimerender/qssgrenderdefaultmaterialshadergenerator.cpp b/src/runtimerender/qssgrenderdefaultmaterialshadergenerator.cpp
index de35c66e..dcf264d3 100644
--- a/src/runtimerender/qssgrenderdefaultmaterialshadergenerator.cpp
+++ b/src/runtimerender/qssgrenderdefaultmaterialshadergenerator.cpp
@@ -365,11 +365,13 @@ static void generateShadowMapOcclusion(QSSGStageGeneratorBase &fragmentShader,
         fragmentShader.addUniform(names.shadowControlStem, "vec4");
         fragmentShader.addUniform(names.shadowMatrixStem, "mat4");
 
+        fragmentShader << "    if (" << names.shadowControlStem << ".y > 0.01) {\n";
         if (inType != QSSGRenderLight::Type::DirectionalLight) {
-            fragmentShader << "    qt_shadow_map_occl = qt_sampleCubemap(" << names.shadowCubeStem << ", " << names.shadowControlStem << ", " << names.shadowMatrixStem << ", " << lightVarNames.lightPos << ".xyz, qt_varWorldPos, vec2(1.0, " << names.shadowControlStem << ".z));\n";
+            fragmentShader << "        qt_shadow_map_occl = qt_sampleCubemap(" << names.shadowCubeStem << ", " << names.shadowControlStem << ", " << names.shadowMatrixStem << ", " << lightVarNames.lightPos << ".xyz, qt_varWorldPos, vec2(1.0, " << names.shadowControlStem << ".z));\n";
         } else {
-            fragmentShader << "    qt_shadow_map_occl = qt_sampleOrthographic(" << names.shadowMapStem << ", " << names.shadowControlStem << ", " << names.shadowMatrixStem << ", qt_varWorldPos, vec2(1.0, " << names.shadowControlStem << ".z));\n";
+            fragmentShader << "        qt_shadow_map_occl = qt_sampleOrthographic(" << names.shadowMapStem << ", " << names.shadowControlStem << ", " << names.shadowMatrixStem << ", qt_varWorldPos, vec2(1.0, " << names.shadowControlStem << ".z));\n";
         }
+        fragmentShader << "    }\n";
     } else {
         fragmentShader << "    qt_shadow_map_occl = 1.0;\n";
     }