Write to gl_FragData instead of gl_FragColor for debug commands if MRT is used

CHANGES.md

@@ -22,6 +22,7 @@ Change Log
 * Fixed KML for when color is an empty string [#4826](https://github.com/AnalyticalGraphicsInc/cesium/pull/4826)
 * Added support for WMS version 1.3 by using CRS vice SRS query string parameter to request projection. SRS is still used for older versions.
 * The attribute `perInstanceAttribute` of `DebugAppearance` has been made optional and defaults to `false`.
+* Fixed a bug that would cause a crash when `debugShowFrustums` is enabled with OIT [#4864](https://github.com/AnalyticalGraphicsInc/cesium/pull/4864)
 
 ### 1.29 - 2017-01-02
 * Improved 3D Models

Source/Scene/Scene.js

@@ -1433,22 +1433,38 @@ define([
         var sp = defaultValue(shaderProgram, command.shaderProgram);
         var fs = sp.fragmentShaderSource.clone();
 
+        var targets = [];
         fs.sources = fs.sources.map(function(source) {
             source = ShaderSource.replaceMain(source, 'czm_Debug_main');
+            var re = /gl_FragData\[(\d+)\]/g;
+            var match;
+            while ((match = re.exec(source)) !== null) {
+                if (targets.indexOf(match[1]) === -1) {
+                    targets.push(match[1]);
+                }
+            }
             return source;
         });
+        var length = targets.length;
 
         var newMain =
             'void main() \n' +
             '{ \n' +
             '    czm_Debug_main(); \n';
 
+        var i;
         if (scene.debugShowCommands) {
             if (!defined(command._debugColor)) {
                 command._debugColor = Color.fromRandom();
             }
             var c = command._debugColor;
-            newMain += '    gl_FragColor.rgb *= vec3(' + c.red + ', ' + c.green + ', ' + c.blue + '); \n';
+            if (length > 0) {
+                for (i = 0; i < length; ++i) {
+                    newMain += '    gl_FragData[' + targets[i] + '].rgb *= vec3(' + c.red + ', ' + c.green + ', ' + c.blue + '); \n';
+                }
+            } else {
+                newMain += '    ' + 'gl_FragColor' + '.rgb *= vec3(' + c.red + ', ' + c.green + ', ' + c.blue + '); \n';
+            }
         }
 
         if (scene.debugShowFrustums) {
@@ -1457,7 +1473,13 @@ define([
             var r = (command.debugOverlappingFrustums & (1 << 0)) ? '1.0' : '0.0';
             var g = (command.debugOverlappingFrustums & (1 << 1)) ? '1.0' : '0.0';
             var b = (command.debugOverlappingFrustums & (1 << 2)) ? '1.0' : '0.0';
-            newMain += '    gl_FragColor.rgb *= vec3(' + r + ', ' + g + ', ' + b + '); \n';
+            if (length > 0) {
+                for (i = 0; i < length; ++i) {
+                    newMain += '    gl_FragData[' + targets[i] + '].rgb *= vec3(' + r + ', ' + g + ', ' + b + '); \n';
+                }
+            } else {
+                newMain += '    ' + 'gl_FragColor' + '.rgb *= vec3(' + r + ', ' + g + ', ' + b + '); \n';
+            }
         }
 
         newMain += '}';

Specs/Scene/SceneSpec.js

@@ -873,4 +873,48 @@ defineSuite([
         expect(s.maximumCubeMapSize).toBeGreaterThanOrEqualTo(16);
         s.destroyForSpecs();
     });
+
+    it('does not throw with debugShowCommands', function() {
+        var s = createScene();
+        if (s.context.drawBuffers) {
+            s.debugShowCommands = true;
+
+            var rectangle = Rectangle.fromDegrees(-100.0, 30.0, -90.0, 40.0);
+
+            var rectanglePrimitive = createRectangle(rectangle, 1000.0);
+            rectanglePrimitive.appearance.material.uniforms.color = new Color(1.0, 0.0, 0.0, 0.5);
+
+            var primitives = s.primitives;
+            primitives.add(rectanglePrimitive);
+
+            s.camera.setView({ destination : rectangle });
+
+            expect(function() {
+                s.renderForSpecs();
+            }).not.toThrowRuntimeError();
+        }
+        s.destroyForSpecs();
+    });
+
+    it('does not throw with debugShowFrustums', function() {
+        var s = createScene();
+        if (s.context.drawBuffers) {
+            s.debugShowFrustums = true;
+
+            var rectangle = Rectangle.fromDegrees(-100.0, 30.0, -90.0, 40.0);
+
+            var rectanglePrimitive = createRectangle(rectangle, 1000.0);
+            rectanglePrimitive.appearance.material.uniforms.color = new Color(1.0, 0.0, 0.0, 0.5);
+
+            var primitives = s.primitives;
+            primitives.add(rectanglePrimitive);
+
+            s.camera.setView({ destination : rectangle });
+
+            expect(function() {
+                s.renderForSpecs();
+            }).not.toThrowRuntimeError();
+        }
+        s.destroyForSpecs();
+    });
 }, 'WebGL');