Basic (non-sorted) transparent rendering and cleanup in RenderSystem

ECS/Components/Mesh.h

@@ -47,7 +47,7 @@ struct Mesh {
         glBindVertexArray(0);
     }
 
-    void render() {
+    void render() const {
         glBindVertexArray(VAO);
         glBindBuffer(GL_ARRAY_BUFFER, VBO);
         glDrawElements(GL_TRIANGLES, vertex_count, GL_UNSIGNED_INT, 0);

ECS/Components/Texture.h

@@ -8,30 +8,53 @@
 #include "../../Util/stb_image.h"
 
 struct Texture {
-    explicit Texture(const std::string& path) {
+    struct Settings {
+        Settings(bool mipmaps, bool transparent) : mipmaps(mipmaps), transparent(transparent) {}
+
+        bool mipmaps = true;
+        bool transparent = false;
+    };
+
+    explicit Texture(const std::string& path, Settings settings) {
         glGenTextures(1, &id);
         glBindTexture(GL_TEXTURE_2D, id);
 
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
 
-        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); // Mipmapping
+        if (settings.mipmaps) {
+            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+        } else {
+            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        }
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
         int width, height, nrChannels;
         unsigned char *data = stbi_load(path.c_str(), &width, &height, &nrChannels, 0);
 
         if (data) {
-            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
-            glGenerateMipmap(GL_TEXTURE_2D); // Mipmapping
+            // Alpha channel?
+            unsigned int glChannels = GL_RGB;
+            if (nrChannels == 4) {
+                glChannels = GL_RGBA;
+            }
+
+            glTexImage2D(GL_TEXTURE_2D, 0, glChannels, width, height, 0, glChannels, GL_UNSIGNED_BYTE, data);
+
+            if (settings.mipmaps) {
+                glGenerateMipmap(GL_TEXTURE_2D);
+            }
         } else {
             std::cout << "Failed to load texture" << std::endl;
         }
 
         stbi_image_free(data);
+
+        render_transparent = settings.transparent;
     }
 
     unsigned int id;
+    bool render_transparent = false;
 };
 
 #endif //ECSGAME_TEXTURE_H

ECS/Systems/RenderSystem.h

@@ -28,29 +28,48 @@ public:
             shader.setMat4("projection", camera->projection);
             shader.setMat4("view", glm::inverse(cameraTransform->matrix));
 
+            std::vector<RenderObject> renderObjects;
+
             pWorld->each<Mesh, Transform>([&](Entity *ent, ComponentHandle<Mesh> mesh, ComponentHandle<Transform> transform) {
-                shader.setMat4("model", transform->matrix);
-
-                mesh->render();
+                renderObjects.emplace_back(RenderObject(transform->matrix, 0, mesh.get()));
             });
 
-            // TODO: Duplicate of loop above, but for ObjMesh instead of Mesh. Is it possible to do this implicitly via polymorphism?
+            // TODO: Is it possible to do get ObjMeshes in the Mesh loop above implicitly via polymorphism?
             pWorld->each<ObjMesh, Transform>([&](Entity *ent, ComponentHandle<ObjMesh> mesh, ComponentHandle<Transform> transform) {
-                shader.setMat4("model", transform->matrix);
-
-                mesh->render();
+                renderObjects.emplace_back(RenderObject(transform->matrix, 0, mesh.get()));
             });
 
-            // Render ObjMeshes with textures
+            // ObjMesh with textures
             pWorld->each<ObjMesh, Transform, Texture>([&](Entity *ent, ComponentHandle<ObjMesh> mesh, ComponentHandle<Transform> transform, ComponentHandle<Texture> texture) {
-                shader.setMat4("model", transform->matrix);
-                glBindTexture(GL_TEXTURE_2D, texture->id);
-
-                mesh->render();
+                renderObjects.emplace_back(RenderObject(transform->matrix, texture->id, mesh.get()));
             });
+
+            // TODO: Separate lists for transparent and non-transparent RenderObjects. The non-transparent list is
+            //  rendered first, then the transparent list is sorted and rendered.
+
+            for (const RenderObject &obj : renderObjects) {
+                shader.setMat4("model", obj.matrix);
+
+                // 0 can't be a valid texture name, so we use it for meshes without textures here
+                if (obj.texture_id != 0) {
+                    glBindTexture(GL_TEXTURE_2D, obj.texture_id);
+                }
+
+                obj.mesh.render();
+            }
         });
     }
 
+    struct RenderObject {
+        RenderObject(const glm::mat4 &matrix, unsigned int textureId, const Mesh &mesh) : matrix(matrix),
+                                                                                          texture_id(textureId),
+                                                                                          mesh(mesh) {}
+
+        glm::mat4 matrix;
+        unsigned int texture_id;
+        Mesh mesh;
+    };
+
 private:
     float gravityAmount;
 };

Shaders/default-fragment.fs

@@ -2,10 +2,17 @@
 out mediump vec4 FragColor;
 
 in mediump vec2 TexCoord;
+in mediump vec3 Normal;
 
-uniform sampler2D ourTexture;
+uniform sampler2D tex;
 
 void main()
 {
-    FragColor = texture(ourTexture, TexCoord);
+    mediump vec4 texColor = texture(tex, TexCoord);
+
+    // Alpha Scissors
+    if(texColor.a < 0.1)
+        discard;
+
+    FragColor = texColor;
 }

Shaders/default-vertex.vs

@@ -4,6 +4,7 @@ layout (location = 1) in vec3 NORMAL;
 layout (location = 2) in vec2 UV;
 
 out vec2 TexCoord;
+out vec3 Normal;
 
 uniform mat4 model;
 uniform mat4 view;
@@ -13,4 +14,5 @@ void main()
 {
     gl_Position = projection * view * model * vec4(aPos, 1.0);
     TexCoord = UV;
+    Normal = NORMAL;
 }

main.cpp

@@ -33,6 +33,7 @@ static void mouse_callback(GLFWwindow* window, double xpos, double ypos) {
 }
 
 int main() {
+    // TODO: Move this to RenderSystem?
     GLFWwindow *window;
 
     /* Initialize the library */
@@ -65,6 +66,10 @@ int main() {
 
     glEnable(GL_DEPTH_TEST);
 
+    // Transparency
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
     // TODO: Could be automated by getting all classes within 'ECS/Systems'
     // world->registerSystem(new GravitySystem(-9.8f));
     // world->registerSystem(new PositionDebugOutputSystem());
@@ -83,7 +88,7 @@ int main() {
     Entity *box2 = world->create();
     box2->assign<Transform>();
     box2->assign<ObjMesh>("Resources/Monkey.obj");
-    box2->assign<Texture>("Resources/tex.jpg");
+    box2->assign<Texture>("Resources/tex.png", Texture::Settings(true, true));
     box2->get<Transform>()->translate(glm::vec3(0.0f, 0.0f, -5.0f));
 
     Shader defaultShader("Shaders/default-vertex.vs", "Shaders/default-fragment.fs");