[#69] Make particles camera facing, to avoid invisible particles from certain angles

modules/camera/src/vkcv/camera/Camera.cpp

@@ -38,8 +38,15 @@ namespace vkcv::camera {
 		m_view = view;
 	}
 
+    const glm::mat4 y_correction(
+        1.0f, 0.0f, 0.0f, 0.0f,
+        0.0f, -1.0f, 0.0f, 0.0f,
+        0.0f, 0.0f, 1.0f, 0.0f,
+        0.0f, 0.0f, 0.0f, 1.0f
+    );
+
     const glm::mat4& Camera::getProjection() const {
-        return m_projection;
+        return y_correction * m_projection;
     }
 
     void Camera::setProjection(const glm::mat4& projection) {
@@ -47,13 +54,6 @@ namespace vkcv::camera {
     }
 
     glm::mat4 Camera::getMVP() const {
-		const glm::mat4 y_correction (
-				1.0f,  0.0f,  0.0f,  0.0f,
-				0.0f, -1.0f,  0.0f,  0.0f,
-				0.0f,  0.0f,  1.0f,  0.0f,
-				0.0f,  0.0f,  0.0f,  1.0f
-		);
-    	
         return y_correction * m_projection * m_view;
     }
 

projects/particle_simulation/shaders/shader.vert

@@ -19,7 +19,8 @@ layout(std430, binding = 2) coherent buffer buffer_inParticle
 };
 
 layout( push_constant ) uniform constants{
-    mat4 mvp;
+    mat4 view;
+    mat4 projection;
 };
 
 layout(location = 1) out vec3 passVelocity;
@@ -30,6 +31,10 @@ void main()
     int id = gl_InstanceIndex;
     passVelocity = inParticle[id].velocity;
     passlifeTime = inParticle[id].lifeTime;
-    vec3 moved_particle = particle + inParticle[id].position;
-	gl_Position =   mvp * vec4(moved_particle, 1.0);
+    // particle position in view space
+    vec4 positionView = view * vec4(inParticle[id].position, 1);
+    // by adding the triangle position in view space the mesh is always camera facing
+    positionView.xyz += particle;
+    // multiply with projection matrix for final position
+	gl_Position =   projection * positionView;
 }
\ No newline at end of file

projects/particle_simulation/src/main.cpp

@@ -224,9 +224,11 @@ int main(int argc, const char **argv) {
 //        particleSystem.updateParticles(deltatime);
 
         cameraManager.update(deltatime);
-        std::vector<glm::mat4> mvp;
-        mvp.clear();
-        mvp.push_back( cameraManager.getActiveCamera().getMVP());
+
+        // split view and projection to allow for easy billboarding in shader
+        glm::mat4 renderingMatrices[2];
+        renderingMatrices[0] = cameraManager.getActiveCamera().getView();
+        renderingMatrices[1] = cameraManager.getActiveCamera().getProjection();
 
         auto cmdStream = core.createCommandStream(vkcv::QueueType::Graphics);
         float random = rdm(rdmEngine);
@@ -242,7 +244,7 @@ int main(int argc, const char **argv) {
 
         core.recordBufferMemoryBarrier(cmdStream, particleBuffer.getHandle());
 
-        vkcv::PushConstantData pushConstantDataDraw((void *) mvp.data(), sizeof(glm::mat4));
+        vkcv::PushConstantData pushConstantDataDraw((void *) &renderingMatrices[0], 2 * sizeof(glm::mat4));
         core.recordDrawcallsToCmdStream(
                 cmdStream,
                 particlePass,