Use a fullscreen pass for skybox

data/shaders/sky.frag

@@ -4,7 +4,7 @@ out vec4 FragColor;
 
 void main(void)
 {
-    vec3 eyedir = gl_FragCoord.xyz / vec3(screen, 1.);
+    vec3 eyedir = vec3(gl_FragCoord.xy / screen, 1.);
     eyedir = 2.0 * eyedir - 1.0;
     vec4 tmp = (InverseProjectionMatrix * vec4(eyedir, 1.));
     tmp /= tmp.w;

data/shaders/sky.vert

@@ -0,0 +1,10 @@
+#if __VERSION__ >= 330
+layout(location = 0) in vec3 Position;
+#else
+in vec3 Position;
+#endif
+
+void main()
+{
+    gl_Position = vec4(Position, 1.);
+}

src/graphics/render_skybox.cpp

@@ -380,27 +380,18 @@ void IrrDriver::renderSkybox(const scene::ICameraSceneNode *camera)
 {
     if (SkyboxTextures.empty())
         return;
-    glBindVertexArray(MeshShader::SkyboxShader::getInstance()->cubevao);
     glEnable(GL_DEPTH_TEST);
     glDisable(GL_CULL_FACE);
     assert(SkyboxTextures.size() == 6);
 
-    core::matrix4 translate;
-    translate.setTranslation(camera->getAbsolutePosition());
-
-    // Draw the sky box between the near and far clip plane
-    const f32 viewDistance = (camera->getNearValue() + camera->getFarValue()) * 0.5f;
-    core::matrix4 scale;
-    scale.setScale(core::vector3df(viewDistance, viewDistance, viewDistance));
-    core::matrix4 transform = translate * scale;
-    core::matrix4 invtransform;
-    transform.getInverse(invtransform);
     glDisable(GL_BLEND);
 
     glUseProgram(MeshShader::SkyboxShader::getInstance()->Program);
-    MeshShader::SkyboxShader::getInstance()->setUniforms(transform);
+    glBindVertexArray(MeshShader::SkyboxShader::getInstance()->vao);
+    MeshShader::SkyboxShader::getInstance()->setUniforms();
+
     MeshShader::SkyboxShader::getInstance()->SetTextureUnits(SkyboxCubeMap);
 
-    glDrawElements(GL_TRIANGLES, 6 * 6, GL_UNSIGNED_INT, 0);
+    glDrawArrays(GL_TRIANGLES, 0, 3);
     glBindVertexArray(0);
 }

src/graphics/shaders.cpp

@@ -336,66 +336,19 @@ static void initBillboardVBO()
     glBufferData(GL_ARRAY_BUFFER, 16 * sizeof(float), quad, GL_STATIC_DRAW);
 }
 
-GLuint SharedObject::cubevbo = 0;
-GLuint SharedObject::cubeindexes = 0;
+GLuint SharedObject::skytrivbo = 0;
 
-static void initCubeVBO()
+static void initSkyTriVBO()
 {
-    // From CSkyBoxSceneNode
-    float corners[] =
-        {
-            // top side
-            1., 1., -1.,
-            1., 1., 1.,
-            -1., 1., 1.,
-            -1., 1., -1.,
+  const float tri_vertex[] = {
+      -1., -1., 1.,
+      -1., 3., 1.,
+      3., -1., 1.,
+  };
 
-            // Bottom side
-            1., -1., 1.,
-            1., -1., -1.,
-            -1., -1., -1.,
-            -1., -1., 1.,
-
-            // right side
-            1., -1, -1,
-            1., -1, 1,
-            1., 1., 1.,
-            1., 1., -1.,
-
-            // left side
-            -1., -1., 1.,
-            -1., -1., -1.,
-            -1., 1., -1.,
-            -1., 1., 1.,
-
-            // back side
-            -1., -1., -1.,
-            1., -1, -1.,
-            1, 1, -1.,
-            -1, 1, -1.,
-
-            // front side
-            1., -1., 1.,
-            -1., -1., 1.,
-            -1, 1., 1.,
-            1., 1., 1.,
-        };
-    int indices[] = {
-        0, 1, 2, 2, 3, 0,
-        4, 5, 6, 6, 7, 4,
-        8, 9, 10, 10, 11, 8,
-        12, 13, 14, 14, 15, 12,
-        16, 17, 18, 18, 19, 16,
-        20, 21, 22, 22, 23, 20
-    };
-
-    glGenBuffers(1, &SharedObject::cubevbo);
-    glBindBuffer(GL_ARRAY_BUFFER, SharedObject::cubevbo);
-    glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 3 * sizeof(float), corners, GL_STATIC_DRAW);
-
-    glGenBuffers(1, &SharedObject::cubeindexes);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, SharedObject::cubeindexes);
-    glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6 * 6 * sizeof(int), indices, GL_STATIC_DRAW);
+    glGenBuffers(1, &SharedObject::skytrivbo);
+    glBindBuffer(GL_ARRAY_BUFFER, SharedObject::skytrivbo);
+    glBufferData(GL_ARRAY_BUFFER, 3 * 3 * sizeof(float), tri_vertex, GL_STATIC_DRAW);
 }
 
 GLuint SharedObject::frustrumvbo = 0;
@@ -535,7 +488,7 @@ void Shaders::loadShaders()
     initQuadVBO();
     initQuadBuffer();
     initBillboardVBO();
-    initCubeVBO();
+    initSkyTriVBO();
     initFrustrumVBO();
     initShadowVPMUBO();
     initLightingDataUBO();
@@ -1417,17 +1370,16 @@ namespace MeshShader
     SkyboxShader::SkyboxShader()
     {
         Program = LoadProgram(OBJECT,
-            GL_VERTEX_SHADER, file_manager->getAsset("shaders/object_pass.vert").c_str(),
+            GL_VERTEX_SHADER, file_manager->getAsset("shaders/sky.vert").c_str(),
             GL_FRAGMENT_SHADER, file_manager->getAsset("shaders/sky.frag").c_str());
-        AssignUniforms("ModelMatrix");
+        AssignUniforms();
         AssignSamplerNames(Program, 0, "tex");
 
-        glGenVertexArrays(1, &cubevao);
-        glBindVertexArray(cubevao);
-        glBindBuffer(GL_ARRAY_BUFFER, SharedObject::cubevbo);
+        glGenVertexArrays(1, &vao);
+        glBindVertexArray(vao);
+        glBindBuffer(GL_ARRAY_BUFFER, SharedObject::skytrivbo);
         glEnableVertexAttribArray(0);
         glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0);
-        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, SharedObject::cubeindexes);
         glBindVertexArray(0);
     }
 

src/graphics/shaders.hpp

@@ -30,7 +30,7 @@ class SharedObject
 {
 public:
     static GLuint billboardvbo;
-    static GLuint cubevbo, cubeindexes, frustrumvbo, frustrumindexes, ParticleQuadVBO;
+    static GLuint skytrivbo, frustrumvbo, frustrumindexes, ParticleQuadVBO;
     static GLuint ViewProjectionMatrixesUBO, LightingDataUBO;
     static GLuint FullScreenQuadVAO;
     static GLuint UIVAO;
@@ -281,11 +281,11 @@ public:
     DisplaceShader();
 };
 
-class SkyboxShader : public ShaderHelperSingleton<SkyboxShader, core::matrix4>, public TextureRead<Trilinear_cubemap>
+class SkyboxShader : public ShaderHelperSingleton<SkyboxShader>, public TextureRead<Trilinear_cubemap>
 {
 public:
     SkyboxShader();
-    GLuint cubevao;
+    GLuint vao;
 };
 
 class NormalVisualizer : public ShaderHelperSingleton<NormalVisualizer, video::SColor>