feat: post-processing effects

src/graphics/core/PostProcessing.cpp

@@ -4,13 +4,15 @@
 #include "Texture.hpp"
 #include "Framebuffer.hpp"
 #include "DrawContext.hpp"
+#include "PostEffect.hpp"
+#include "assets/Assets.hpp"
 
 #include <stdexcept>
 
 PostProcessing::PostProcessing() {
     // Fullscreen quad mesh bulding
     float vertices[] {
-        -1.0f, -1.0f, -1.0f, 1.0f, 1.0f, 1.0f,
+        -1.0f, -1.0f, -1.0f, 1.0f, 1.0f,  1.0f,
         -1.0f, -1.0f,  1.0f, 1.0f, 1.0f, -1.0f
     };
     VertexAttribute attrs[] {{2}, {0}};
@@ -23,22 +25,56 @@ void PostProcessing::use(DrawContext& context) {
     const auto& vp = context.getViewport();
     if (fbo) {
         fbo->resize(vp.x, vp.y);
+        fboSecond->resize(vp.x, vp.y);
     } else {
         fbo = std::make_unique<Framebuffer>(vp.x, vp.y);
+        fboSecond = std::make_unique<Framebuffer>(vp.x, vp.y);
     }
     context.setFramebuffer(fbo.get());
 }
 
-void PostProcessing::render(const DrawContext& context, Shader* screenShader) {
+void PostProcessing::render(
+    const DrawContext& context, const Assets& assets, float timer
+) {
     if (fbo == nullptr) {
         throw std::runtime_error("'use(...)' was never called");
     }
+    int totalPasses = 0;
+    for (const auto& effect : effectSlots) {
+        totalPasses += (effect != nullptr && effect->isActive());
+    }
 
-    const auto& viewport = context.getViewport();
-    screenShader->use();
-    screenShader->uniform2i("u_screenSize", viewport);
-    fbo->getTexture()->bind();
-    quadMesh->draw();
+    if (totalPasses == 0) {
+        auto& effect = assets.require<PostEffect>("default");
+        effect.use();
+        fbo->getTexture()->bind();
+        quadMesh->draw();
+        return;
+    }
+
+    int currentPass = 1;
+    for (const auto& effect : effectSlots) {
+        if (effect == nullptr || !effect->isActive()) {
+            continue;
+        }
+        auto& shader = effect->use();
+
+        const auto& viewport = context.getViewport();
+        shader.uniform1i("u_screen", 0);
+        shader.uniform2i("u_screenSize", viewport);
+        shader.uniform1f("u_timer", timer);
+
+        fbo->getTexture()->bind();
+        if (currentPass < totalPasses) {
+            fboSecond->bind();
+        }
+        quadMesh->draw();
+        if (currentPass < totalPasses) {
+            fboSecond->unbind();
+            std::swap(fbo, fboSecond);
+        }
+        currentPass++;
+    }
 }
 
 std::unique_ptr<ImageData> PostProcessing::toImage() {