Tutorial #3 - Visualización 3D

Uso de matrices para visualizar un cubo 3D

Author: devcarmelo

.gitignore

@@ -73,3 +73,5 @@ $RECYCLE.BIN/
 
 # Windows shortcuts
 *.lnk
+
+BUILDS/

CMakeLists.txt

@@ -19,3 +19,4 @@ set(GRAPHIC_LIBS ${OPENGL_gl_LIBRARY} ${GLEW_LIBRARIES} ${GLFW3_LIBRARY})
 add_subdirectory(Tutorial-00)
 add_subdirectory(Tutorial-01)
 add_subdirectory(Tutorial-02)
+add_subdirectory(Tutorial-03)

Common/OpenGLShader.hpp

@@ -160,6 +160,10 @@ class OpenGLShader {
         glUseProgram(program);
     }
 
+	void unUse() {
+		glUseProgram(0);
+	}
+
 private:
     GLuint program;
 };

Common/OpenGLWindow.hpp

@@ -18,6 +18,8 @@ class OpenGLWindow {
 	{ }
 
 	bool init(string title, int width = 1024, int height = 720, bool full_screen = false) {
+		aspect_ratio = static_cast<float>(width) / static_cast<float>(height);
+
 		glfwSetErrorCallback(error_callback);
 
 		if (!glfwInit()) return false;

Tutorial-01/CMakeLists.txt

@@ -3,6 +3,7 @@ file(COPY simple.vertex_shader simple.fragment_shader DESTINATION shaders)
 add_executable( Tutorial-01 shader-opengl.cpp 
 							shaders/simple.vertex_shader
 							shaders/simple.fragment_shader
-							../common/openglwindow.hpp )
+							../common/openglwindow.hpp
+							../common/openglshader.hpp )
 
 target_link_libraries( Tutorial-01 ${GRAPHIC_LIBS} )

Tutorial-02/CMakeLists.txt

@@ -3,6 +3,7 @@ file(COPY simple.vertex_shader simple.fragment_shader DESTINATION shaders)
 add_executable( Tutorial-02 data-opengl.cpp 
 							shaders/simple.vertex_shader
 							shaders/simple.fragment_shader
-							../common/openglwindow.hpp )
+							../common/openglwindow.hpp
+							../common/openglshader.hpp )
 
 target_link_libraries( Tutorial-02 ${GRAPHIC_LIBS} )

Tutorial-03/3D-OpenGL.cpp

@@ -0,0 +1,140 @@
+#include "OpenGLWindow.hpp"
+#include "OpenGLShader.hpp"
+
+#include <glm/gtc/matrix_transform.hpp>
+
+class Tutorial_03 : public OpenGLWindow {
+
+public:
+	Tutorial_03() : vao{}, buffer{}, index_buffer{}, MatrixID{} { }
+
+private:
+	void onstart() override {
+		// crear, compilar y enlasar el Vertex y Fragment Shader
+		GLuint program = shader_simple.compile("shaders/simple.vertex_shader", "shaders/simple.fragment_shader");
+
+		// Obtener el ID del uniform llamado "MVP"
+		MatrixID = glGetUniformLocation(program, "MVP");
+
+		// crear y enlazar un vao
+		glGenVertexArrays(1, &vao);
+		glBindVertexArray(vao);
+
+		// vetices para generar un cubo 3D
+		static const float vertex[] =
+		{
+			 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, -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
+		};
+
+		// componetes RGBA para los colores de cada vertice
+		static const float color[] =
+		{
+			1.0f, 0.0f, 0.0f, 1.0f,
+			0.0f, 1.0f, 0.0f, 1.0f,
+			0.0f, 0.0f, 1.0f, 1.0f,
+			1.0f, 0.0f, 0.0f, 1.0f,
+			0.0f, 1.0f, 0.0f, 1.0f,
+			1.0f, 0.0f, 0.0f, 1.0f,
+			0.0f, 1.0f, 0.0f, 1.0f,
+			0.0f, 0.0f, 1.0f, 1.0f
+		};
+
+		// indices usados para unir los vertices que componen el cubo
+		static const GLushort indices[] =
+		{
+			0, 1, 2,
+			7, 6, 5,
+			4, 5, 1,
+			5, 6, 2,
+			6, 7, 3,
+			0, 3, 7,
+			3, 0, 2,
+			4, 7, 5,
+			0, 4, 1,
+			1, 5, 2,
+			2, 6, 3,
+			4, 0, 7
+		};
+
+		// generar, almacenar el buffer de indices 
+		glGenBuffers(1, &index_buffer);
+		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer);
+		glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
+
+		// generar dos ids para los buffer
+		glGenBuffers(2, buffer);
+
+		// enlazar el buffer de vertices
+		glBindBuffer(GL_ARRAY_BUFFER, buffer[0]);
+		// almacenar datos en el buffer de vertices
+		glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW);
+
+		// describir los datos y activar vPosition (location = 0)
+		glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, NULL);
+		glEnableVertexAttribArray(0);
+
+		// enlazar el buffer de color
+		glBindBuffer(GL_ARRAY_BUFFER, buffer[1]);
+		// almacenar datos en el buffer de color
+		glBufferData(GL_ARRAY_BUFFER, sizeof(color), color, GL_STATIC_DRAW);
+
+		// describir los datos y activar vColor (location = 1)
+		glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, NULL);
+		glEnableVertexAttribArray(1);
+	}
+
+	void onrender(double time) override {
+		glClear(GL_COLOR_BUFFER_BIT);
+		glEnable(GL_CULL_FACE);
+
+		// Usar el shader
+		shader_simple.use();
+		
+		// Matriz de modelo, se aplica una rotacion sobre el eje Y 
+		glm::mat4 Model = glm::rotate(glm::mat4(1.0f), (float)time, glm::vec3(0.0f, 1.0f, 0.0f));
+
+		// Matriz de proyeccion y visualizacion
+		glm::mat4 Projection = glm::perspective(45.0f, aspect_ratio, 0.1f, 100.0f);
+		glm::mat4 View = glm::lookAt(glm::vec3(4, 3, -3), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
+
+		// Crear la matriz total MVP
+		glm::mat4 MVP = Projection * View * Model;
+		
+		// Enviar las tranformaciones al shader
+		// MatrixID es el ID del uniform MVP obtenida por glGetUniformLocation(program, "MVP");
+		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
+
+		// Dibujar cubo usando los indices almacenados en el buffer,
+		// 1 triangulo = 3 indices, 1 cara = 2 triangulos, 1 cubo = 6 caras.
+		// 3 * 2 * 6 = 36 indices a dibujar 
+		glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_SHORT, 0);
+	}
+
+	// Liberar memoria usada por los buffers
+	void onstop() override {
+		glDeleteBuffers(2, buffer);
+		glDeleteBuffers(1, &index_buffer);
+		glDeleteVertexArrays(1, &vao);
+	}
+
+	OpenGLShader shader_simple;
+	GLuint vao, index_buffer;
+	GLuint buffer[2];
+	GLuint MatrixID;
+};
+
+int main() {
+	Tutorial_03 win_app;
+	if (win_app.init("OpenGL Moderno - Visualizar 3D", 1280, 720)) {
+		win_app.info();
+		win_app.run();
+	}
+	return 0;
+}

Tutorial-03/CMakeLists.txt

@@ -0,0 +1,9 @@
+file(COPY simple.vertex_shader simple.fragment_shader DESTINATION shaders)
+
+add_executable( Tutorial-03 3d-opengl.cpp 
+							shaders/simple.vertex_shader
+							shaders/simple.fragment_shader
+							../common/openglwindow.hpp 
+							../common/openglshader.hpp )
+							
+target_link_libraries( Tutorial-03 ${GRAPHIC_LIBS} )

Tutorial-03/simple.fragment_shader

@@ -0,0 +1,9 @@
+#version 330 core
+
+in vec4 color;
+out vec4 fColor;
+
+void main()
+{
+	fColor = color;
+}

Tutorial-03/simple.vertex_shader

@@ -0,0 +1,14 @@
+#version 330 core
+
+layout (location = 0) in vec4 vPosition;
+layout (location = 1) in vec4 vColor;
+
+uniform mat4 MVP;
+
+out vec4 color;
+
+void main()
+{
+     gl_Position = MVP * vPosition;
+	 color = vColor; 
+}