Improved openGL and ImGUI implementation

include/particle.h

@@ -0,0 +1,69 @@
+#ifndef PARTICLE_H
+#define PARTICLE_H
+
+#include <stdlib.h>
+
+#define G_CONSTANT 9.807f
+
+typedef struct {
+	float x, y, z;
+} Vec3;
+
+typedef struct {
+	float r, g, b, a;
+} Color;
+
+typedef struct {
+	Vec3 position;
+	Vec3 velocity;
+	Color color;
+
+	float life;
+} Particle;
+
+// INFO: This adds adder to out, basicaly out + adder
+void vec_add(Vec3 &out, Vec3 adder) {
+	out.x += adder.x;
+	out.y += adder.y;
+	out.z += adder.z;
+}
+
+Particle particle_init(Vec3 position, Color color) {
+	Particle p;
+	p.position = position;
+	p.color = color;
+	p.velocity = {0.0f, 0.0f, 0.0f};
+
+	p.life = 10;
+	return p;
+}
+
+int particle_update(Particle *particles, unsigned long long size, float time) {
+	int alive_count = 0;
+	for (unsigned long long i = 0; i < size; i++) {
+		Particle p = particles[i];
+		if (p.life == 0) {
+			particles[i].position = {0.0f, 0.0f, 0.0f};                        // Start at center
+			particles[i].velocity = {(rand() % 100 - 50) / 50.0f, 5.0f, 0.0f}; // Random spray up
+			particles[i].life = 2.0f;                                          // Give it 2 seconds of life
+			continue;
+		}
+
+		p.velocity.y += (G_CONSTANT * time);
+
+		p.position.x += p.velocity.x * time;
+		p.position.y += p.velocity.y * time;
+		p.position.z += p.velocity.z * time;
+
+		vec_add(p.position, (p.velocity));
+
+        if (p.life > 0) p.life -= time;
+
+		particles[i] = p;
+		alive_count++;
+	}
+
+	return alive_count;
+}
+
+#endif // PARTICLE_H

source/main.cpp

@@ -1,20 +1,24 @@
 #include "main.h"
 #include "io.h"
+#include "particle.h"
 
 // ImGui includes
 #include "imgui/imgui.h"
 #include "imgui/imgui_impl_glfw.h"
 #include "imgui/imgui_impl_opengl3.h"
+#include <cstdio>
 
 const char FRAGMENT_SHADER_SOURCE[] = "./source/shader/fragment.glsl";
 const char VERTEX_SHADER_SOURCE[] = "./source/shader/vertex.glsl";
 
-const char PROGRAM_NAME[] = "OpenGL Template";
+const char PROGRAM_NAME[] = "Particle Sim";
 
 const unsigned int SCR_WIDTH = 1920;
 const unsigned int SCR_HEIGHT = 1080;
 const char *glsl_version;
 
+const unsigned int PARTICLE_COUNT = 1000;
+
 GLFWwindow *window;
 unsigned int VBO, VAO;
 unsigned int shader;
@@ -56,7 +60,20 @@ __attribute__((constructor)) static void init_glfw(void) {
 	glBindBuffer(GL_ARRAY_BUFFER, VBO);
 
 	glEnableVertexAttribArray(0);
-	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
+
+	// Position: 3 floats, starts at 0
+	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 11 * sizeof(float), (void *)0);
+	glEnableVertexAttribArray(0);
+
+	// Color: 4 floats, starts after 6 floats (Position + Velocity)
+	glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 11 * sizeof(float), (void *)(6 * sizeof(float)));
+	glEnableVertexAttribArray(1);
+
+	// Life: 1 float, starts after 10 floats (Position + Velocity + Color)
+	glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, 11 * sizeof(float), (void *)(10 * sizeof(float)));
+	glEnableVertexAttribArray(2);
+
+	glBufferData(GL_ARRAY_BUFFER, sizeof(Particle) * PARTICLE_COUNT, NULL, GL_DYNAMIC_DRAW);
 
 	char *vertex_shader_source = read_file(VERTEX_SHADER_SOURCE);
 	char *fragment_shader_source = read_file(FRAGMENT_SHADER_SOURCE);
@@ -84,31 +101,51 @@ __attribute__((constructor)) static void init_glfw(void) {
 __attribute__((destructor)) static void shutdown_glfw(void) {
 	glDeleteVertexArrays(1, &VAO);
 	glDeleteBuffers(1, &VBO);
-    glfwDestroyWindow(window);
+	glfwDestroyWindow(window);
 	glfwTerminate();
 }
 
 static inline void init_imgui() {
-    IMGUI_CHECKVERSION();
-    ImGui::CreateContext();
-    ImGui::StyleColorsDark();
-    ImGui_ImplGlfw_InitForOpenGL(window, true);
-    ImGui_ImplOpenGL3_Init(glsl_version);
+	IMGUI_CHECKVERSION();
+	ImGui::CreateContext();
+	ImGui::StyleColorsDark();
+	ImGui_ImplGlfw_InitForOpenGL(window, true);
+	ImGui_ImplOpenGL3_Init(glsl_version);
 }
 
 int main() {
 #ifndef NDEBUG
-    init_imgui();
+	init_imgui();
 #endif
+	Particle *particles = (Particle *)malloc(sizeof(Particle) * PARTICLE_COUNT);
+
+	char errLog[128];
+	if (particles == NULL) {
+		snprintf(errLog, 128, "There was a issue allocating memory for the particle list\n");
+	} else {
+		snprintf(errLog, 128, "Successfully allocated memory for the particle list\n");
+
+		for (unsigned long long i = 0; i < PARTICLE_COUNT; i++) {
+            particles[i] = particle_init({0.0,0.0,0.0}, {1.0,1.0,1.0,1.0});
+            particles[i].life = -1.0f; // Start with imortal particles
+		}
+	}
+
+	float current_time, last_time, delta_time;
+	int alive_count = 0;
 
 	while (!glfwWindowShouldClose(window)) {
+		current_time = static_cast<float>(glfwGetTime());
+		delta_time = current_time - last_time;
+		last_time = current_time;
+
 		// Poll events
 		glfwPollEvents();
 
 #ifndef NDEBUG
-        if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) {
-            glfwSetWindowShouldClose(window, true);
-        }
+		if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) {
+			glfwSetWindowShouldClose(window, true);
+		}
 		// Start ImGui frame
 		ImGui_ImplOpenGL3_NewFrame();
 		ImGui_ImplGlfw_NewFrame();
@@ -117,8 +154,21 @@ int main() {
 		// Create ImGui window
 		ImGui::Begin("Debug");
 		ImGui::Text("FPS: %.1f", static_cast<double>(ImGui::GetIO().Framerate));
+        ImGui::Text("Particle %d: X=%3.2f Y=%3.2f Z=%3.2f",0, particles[0].position.x, particles[0].position.y, particles[0].position.z);
+        ImGui::Text("Thread Status: ");
+        ImGui::TextColored({0.0, 0.7f ,0.0, 1.0}, "READY\n");
+		ImGui::Text("%s", errLog);
 		ImGui::End();
 #endif
+		alive_count = particle_update(particles, PARTICLE_COUNT, delta_time);
+
+		glUseProgram(shader);
+
+		glBindBuffer(GL_ARRAY_BUFFER, VBO);
+		glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Particle) * PARTICLE_COUNT, particles);
+
+		glBindVertexArray(VAO);
+		glDrawArrays(GL_POINTS, 0, alive_count);
 
 		// Render
 		glClearColor(0.03f, 0.03f, 0.03f, 1.0f);
@@ -134,6 +184,6 @@ int main() {
 		glfwSwapBuffers(window);
 	}
 
+	free(particles);
 	return 0;
 }
-

source/shader/vertex.glsl

@@ -1,9 +1,18 @@
 #version 330 core
-layout (location = 0) in vec2 aPos;
+layout(location = 0) in vec3 aPos; // Position
+layout(location = 1) in vec4 aColor; // Color (RGBA)
+layout(location = 2) in float aLife; // Life
 
-out vec3 vColor;
+out vec4 vColor;
 
 void main() {
-    gl_Position = vec4(aPos, 0.0, 1.0);
+    float alpha = aLife;
+    if (aLife > 0.0) {
+        alpha = aLife / 10.0; // Fade mortal particles
+    } else if (aLife < 0.0) {
+        alpha = 1.0; // Eternal particles are fully opaque
+    }
+    vColor = vec4(aColor.rgb, aColor.a * alpha);
+    gl_Position = vec4(aPos, 1.0);
+    gl_PointSize = 10.0; // Make them big enough to see!
 }
-