feat: orthographic triangle

src/triangle.cpp

@@ -2,6 +2,9 @@
 
 #include <iostream>
 
+#include "glm/glm.hpp"
+#include "glm/gtc/matrix_transform.hpp"
+
 Triangle::Triangle(GLuint shaderProgram)
     : _shaderProgram(shaderProgram)
 {
@@ -22,14 +25,24 @@ Triangle::Triangle(GLuint shaderProgram)
 
 void Triangle::render(float time)
 {
+    // Calculate matrices
+    float left = -1.0, right = 1.0, bottom = -1.0, top = 1.0, near = -1.0, far = 1.0;
+    glm::mat4 projection = glm::ortho(left, right, bottom, top, near, far);
+
+    constexpr float angle = glm::radians(50.0);
+    glm::vec3 axis = glm::vec3(0.0, 1.0, 0.0);
+    glm::mat4 model = glm::rotate(glm::mat4(1.0), angle * time, axis);
+
+    glm::mat4 view = glm::mat4(1.0);
+
+    glm::mat4 mvp = projection * model * view;
+
 	glUseProgram(_shaderProgram);
 
-	GLint timeLocation = glGetUniformLocation(_shaderProgram, "_Time");
+    GLint mvpLocation = getShaderUniformLocation("_ModelViewProjectionMatrix");
-	if (timeLocation == -1)
+    glUniformMatrix4fv(mvpLocation, 1, GL_FALSE, &mvp[0][0]);
-	{
+
-		std::cerr << "Could not find uniform: _Time" << std::endl;
+	GLint timeLocation = getShaderUniformLocation("_Time");
-        return;
-	}
 	float timeValue = time;
 	glUniform1f(timeLocation, timeValue);
 
@@ -38,6 +51,18 @@ void Triangle::render(float time)
 	glDrawArrays(GL_TRIANGLES, 0, 3);
 }
 
+GLint Triangle::getShaderUniformLocation(const std::string& uniformName)
+{
+    GLint location = glGetUniformLocation(_shaderProgram, uniformName.c_str());
+    if (location == -1)
+    {
+        std::cerr << "Could not find uniform: " << uniformName << std::endl;
+        return 0;
+    }
+
+    return location;
+}
+
 Triangle::~Triangle()
 {
     glDeleteVertexArrays(1, &_vao);

src/triangle.hpp

@@ -3,6 +3,7 @@
 #include <GL/glew.h>
 
 #include <vector>
+#include <string>
 
 class Triangle
 {
@@ -23,4 +24,6 @@ private:
          0.5, -0.5, 0.0,    // right
          0.0,  0.5, 0.0     // top
 	};
+
+	GLint getShaderUniformLocation(const std::string& uniformName);
 };

vert.glsl

@@ -2,8 +2,11 @@
 
 layout (location = 0) in vec3 aPos;
 
+uniform mat4x4 _ModelViewProjectionMatrix;
+
 void main()
 {
-    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+    vec4 pos = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+    gl_Position = _ModelViewProjectionMatrix * pos;
 }