Compute-Particles: use vec4 in the ParticlesData structure

Since vec3-vec4 padding is not always correctly implemented in all OpenGL GPU
implementations, use vec4 in the struct declaration.

Also slightly improve readibility of the buffer construction code.

Change-Id: I9dfbeb2bcdc0a713e1e0a872f6a5e8cfe50c52a3
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

2 files changed, 9 insertions, 8 deletions

diff --git a/examples/qt3d/compute-particles/ParticlesScene.qml b/examples/qt3d/compute-particles/ParticlesScene.qml
index cbb21f266..e63c6cb91 100644
--- a/examples/qt3d/compute-particles/ParticlesScene.qml
+++ b/examples/qt3d/compute-particles/ParticlesScene.qml
@@ -94,12 +94,13 @@ Entity {
     readonly property int floatSize: 4
 
     function buildParticlesBuffer() {
-        var bufferData = new Float32Array(particlesCount * 4 * 3);
+        var byteSizeOfParticleData = 12;
+        var bufferData = new Float32Array(particlesCount * byteSizeOfParticleData);
         var factor = 500.0;
         for (var i = 0; i < particlesCount; ++i) {
-            var positionIdx = i * 12;
-            var velocityIdx = i * 12 + 4;
-            var colorIdx = i * 12 + 8;
+            var positionIdx = i * byteSizeOfParticleData;
+            var velocityIdx = i * byteSizeOfParticleData + 4;
+            var colorIdx = i * byteSizeOfParticleData + 8;
 
             for (var j = 0; j < 3; ++j) {
                 bufferData[positionIdx + j] = (Math.random() - 0.5) * factor;
diff --git a/examples/qt3d/compute-particles/particles.comp b/examples/qt3d/compute-particles/particles.comp
index 7feaf5fdd..af993bbe2 100644
--- a/examples/qt3d/compute-particles/particles.comp
+++ b/examples/qt3d/compute-particles/particles.comp
@@ -7,9 +7,9 @@ layout (local_size_x = 1024) in;
 
 struct ParticleData
 {
-    vec3 position;
-    vec3 direction;
-    vec3 color;
+    vec4 position;
+    vec4 direction;
+    vec4 color;
 };
 
 // Particles from previouse frame
@@ -29,7 +29,7 @@ void main(void)
     currentParticle.position = currentParticle.position + currentParticle.direction * particleStep;
 
     // Make acceleration more or less point toward the center of the scene
-    vec3 acceleration =  normalize(vec3(0.0) - currentParticle.position) * finalCollisionFactor;
+    vec4 acceleration =  normalize(vec4(0.0) - currentParticle.position) * finalCollisionFactor;
 
     // New velocity = old velocity + acceleration over step duration
     currentParticle.direction = currentParticle.direction + acceleration * particleStep;