Fix sky particles rendering in modern gl3 too, see #2779

data/shaders/alphatest_particle.vert

@@ -1,4 +1,6 @@
 uniform int flips;
+uniform int sky;
+uniform vec3 view_position;
 uniform float billboard;
 
 #ifdef Explicit_Attrib_Location_Usable
@@ -26,6 +28,11 @@ in float anglespeed;
 out vec2 tc;
 out vec4 pc;
 
+vec4 getQuat(float half_sin, float half_cos)
+{
+    return normalize(vec4(vec3(0.0, 1.0, 0.0) * half_sin, half_cos));
+}
+
 void main(void)
 {
     if (size.x == 0.0 && size.y == 0.0)
@@ -42,12 +49,22 @@ void main(void)
     pc = color_lifetime.zyxw;
 
     vec4 viewpos = vec4(0.);
-    if (flips == 1)
+    if (flips == 1 || sky == 1)
     {
-        float angle = lifetime * anglespeed;
-        float sin_a = sin(mod(angle / 2.0, 6.283185307179586));
-        float cos_a = cos(mod(angle / 2.0, 6.283185307179586));
-        vec4 quat = normalize(vec4(vec3(0.0, 1.0, 0.0) * sin_a, cos_a));
+        vec4 quat = vec4(0.0);
+        if (flips == 1)
+        {
+            float angle = lifetime * anglespeed;
+            float sin_a = sin(mod(angle / 2.0, 6.283185307179586));
+            float cos_a = cos(mod(angle / 2.0, 6.283185307179586));
+            quat = getQuat(sin_a, cos_a);
+        }
+        else
+        {
+            vec3 diff = Position - view_position;
+            float angle = atan(diff.x, diff.z);
+            quat = getQuat(sin(angle / -2.0), cos(angle / -2.0));
+        }
         vec3 newquadcorner = vec3(particle_size * quadcorner, 0.0);
         newquadcorner = newquadcorner + 2.0 * cross(cross(newquadcorner,
             quat.xyz) + quat.w * newquadcorner, quat.xyz);

data/shaders/simple_particle.vert

@@ -1,4 +1,6 @@
 uniform int flips;
+uniform int sky;
+uniform vec3 view_position;
 uniform float billboard;
 
 #ifdef Explicit_Attrib_Location_Usable
@@ -26,6 +28,11 @@ in float anglespeed;
 out vec2 tc;
 out vec4 pc;
 
+vec4 getQuat(float half_sin, float half_cos)
+{
+    return normalize(vec4(vec3(0.0, 1.0, 0.0) * half_sin, half_cos));
+}
+
 void main(void)
 {
     if (size.x == 0.0 && size.y == 0.0)
@@ -42,12 +49,22 @@ void main(void)
     pc = color_lifetime.zyxw;
 
     vec4 viewpos = vec4(0.);
-    if (flips == 1)
+    if (flips == 1 || sky == 1)
     {
-        float angle = lifetime * anglespeed;
-        float sin_a = sin(mod(angle / 2.0, 6.283185307179586));
-        float cos_a = cos(mod(angle / 2.0, 6.283185307179586));
-        vec4 quat = normalize(vec4(vec3(0.0, 1.0, 0.0) * sin_a, cos_a));
+        vec4 quat = vec4(0.0);
+        if (flips == 1)
+        {
+            float angle = lifetime * anglespeed;
+            float sin_a = sin(mod(angle / 2.0, 6.283185307179586));
+            float cos_a = cos(mod(angle / 2.0, 6.283185307179586));
+            quat = getQuat(sin_a, cos_a);
+        }
+        else
+        {
+            vec3 diff = Position - view_position;
+            float angle = atan(diff.x, diff.z);
+            quat = getQuat(sin(angle / -2.0), cos(angle / -2.0));
+        }
         vec3 newquadcorner = vec3(particle_size * quadcorner, 0.0);
         newquadcorner = newquadcorner + 2.0 * cross(cross(newquadcorner,
             quat.xyz) + quat.w * newquadcorner, quat.xyz);

src/graphics/cpu_particle_manager.cpp

@@ -32,7 +32,8 @@
 // ============================================================================
 /** A Shader to render particles.
 */
-class ParticleRenderer : public TextureShader<ParticleRenderer, 2, int, float>
+class ParticleRenderer : public TextureShader
+    <ParticleRenderer, 2, int, int, core::vector3df, float>
 {
 public:
     ParticleRenderer()
@@ -40,7 +41,7 @@ public:
         loadProgram(PARTICLES_RENDERING,
                     GL_VERTEX_SHADER,   "simple_particle.vert",
                     GL_FRAGMENT_SHADER, "simple_particle.frag");
-        assignUniforms("flips", "billboard");
+        assignUniforms("flips", "sky", "view_position", "billboard");
         assignSamplerNames(0, "tex",  ST_TRILINEAR_ANISOTROPIC_FILTERED,
                            1, "dtex", ST_NEAREST_FILTERED);
     }   // ParticleRenderer
@@ -50,7 +51,7 @@ public:
 /** A Shader to render alpha-test particles.
 */
 class AlphaTestParticleRenderer : public TextureShader
-    <AlphaTestParticleRenderer, 1, int, float>
+    <AlphaTestParticleRenderer, 1, int, int, core::vector3df, float>
 {
 public:
     AlphaTestParticleRenderer()
@@ -58,7 +59,7 @@ public:
         loadProgram(PARTICLES_RENDERING,
                     GL_VERTEX_SHADER,   "alphatest_particle.vert",
                     GL_FRAGMENT_SHADER, "alphatest_particle.frag");
-        assignUniforms("flips", "billboard");
+        assignUniforms("flips", "sky", "view_position", "billboard");
         assignSamplerNames(0, "tex",  ST_TRILINEAR_ANISOTROPIC_FILTERED);
     }   // AlphaTestParticleRenderer
 };   // AlphaTestParticleRenderer
@@ -93,6 +94,10 @@ void CPUParticleManager::addParticleNode(STKParticle* node)
     {
         m_flips_material.insert(tex_name);
     }
+    else if (node->isSkyParticle())
+    {
+        m_sky_material.insert(tex_name);
+    }
     m_particles_queue[tex_name].push_back(node);
 }   // addParticleNode
 
@@ -324,9 +329,15 @@ void CPUParticleManager::drawAll()
         });
 
     std::string shader_name;
+    core::vector3df view_position;
+    scene::ICameraSceneNode* cam = irr_driver->getSceneManager()
+        ->getActiveCamera();
+    if (cam)
+        view_position = cam->getPosition();
     for (auto& p : particle_drawn)
     {
         const bool flips = isFlipsMaterial(p.second);
+        const bool sky = m_sky_material.find(p.second) != m_sky_material.end();
         const float billboard = p.second.substr(0, 4) == "_bb_" ? 1.0f : 0.0f;
         Material* cur_mat = p.first;
         if (cur_mat->getShaderName() != shader_name)
@@ -372,14 +383,15 @@ void CPUParticleManager::drawAll()
                 (cur_mat->getTexture()->getTextureHandler(),
                 CVS->isDeferredEnabled() ?
                 irr_driver->getDepthStencilTexture() : 0);
-            ParticleRenderer::getInstance()->setUniforms(flips, billboard);
+            ParticleRenderer::getInstance()->setUniforms(flips, sky,
+                view_position, billboard);
         }
         else
         {
             AlphaTestParticleRenderer::getInstance()->setTextureUnits
                 (cur_mat->getTexture()->getTextureHandler());
-            AlphaTestParticleRenderer::getInstance()->setUniforms(flips,
-                billboard);
+            AlphaTestParticleRenderer::getInstance()->setUniforms(flips, sky,
+                view_position, billboard);
         }
         glBindVertexArray(m_gl_particles.at(p.second)->m_vao);
         glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4,

src/graphics/cpu_particle_manager.hpp

@@ -89,7 +89,7 @@ private:
 
     std::unordered_map<std::string, Material*> m_material_map;
 
-    std::unordered_set<std::string> m_flips_material;
+    std::unordered_set<std::string> m_flips_material, m_sky_material;
 
     static GLuint m_particle_quad;
 
@@ -137,6 +137,7 @@ public:
     {
         m_material_map.clear();
         m_flips_material.clear();
+        m_sky_material.clear();
     }
 
 };