opengl超級寶典 第七版學習筆記

環境

• win10
• visual studio2019

第二章

P9 案例1——glClearBufferfv 方法示例

#include "sb7.h"

class my_application : public sb7::application {
public: 
void render(double currentTime) override {
	//四個引數分別代表紅、綠、藍、透明度
	static const GLfloat red[] = { 1.0f, 0.0f, 0.0f, 1.0f };
	glClearBufferfv(GL_COLOR, 0, red);
}
};

呼叫方法的主程式（不同平臺的呼叫方法見sb7.h檔案結尾處）

#include <iostream>
#include "1_sb7.cpp"


int CALLBACK WinMain(HINSTANCE hInstance,
	HINSTANCE hPrevInstance,
	LPSTR lpCmdLine,
	int nCmdShow) {
	my_application* app = new my_application;
	app->run(app); //run方法中通過while回圈呼叫我們的render方法
	delete app;
	return 0;
}

實作效果：

繪制一個點

#include "sb7.h"

class my_application : public sb7::application {
public:
	void render(double currentTime) override {
		glUseProgram(rendering_program);
		glDrawArrays(GL_POINTS, 0, 1);
	}

	virtual void startup() override {
		rendering_program = compile_shaders();
		glCreateVertexArrays(1, &vertex_array_object);
		glBindVertexArray(vertex_array_object);
	}

	virtual void shutdown() override {
		glDeleteVertexArrays(1, &vertex_array_object);
		glDeleteProgram(rendering_program);
		glDeleteVertexArrays(1, &vertex_array_object);
	}

	GLuint compile_shaders() {
		GLuint vertex_shader;
		GLuint fragment_shader;
		GLuint program;

		//source code for vertex shader
		static const GLchar* vertex_shader_source[] = {
			"#version 460 core                              \n"
			"                                               \n"
			"void main(void)                                \n"
			"{                                              \n"
			"	gl_Position = vec4(0.0f, 0.0f, 0.5f, 1.0f); \n"
			"}                                              \n"
		};

		//source code for fragment shader
		static const GLchar* fragment_shader_source[] = {
			"#version 460 core                              \n"
			"out vec4 color;                                \n"
			"                                               \n"
			"void main(void)                                \n"
			"{                                              \n "
			"	color = vec4(0.0f, 0.0f, 1.0f, 1.0f);       \n"
			"}                                              \n"
		};

		//create and compile vertex shader
		vertex_shader = glCreateShader(GL_VERTEX_SHADER); //glCreateShader創建一個空白的著色器物件
		glShaderSource(vertex_shader, 1, vertex_shader_source, NULL); //glShaderSource將著色器源代碼傳遞給著色器物件
		glCompileShader(vertex_shader); //對著色器物件中包含的任何我源代碼進行編譯

		//create and compile fragment shader
		fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
		glShaderSource(fragment_shader, 1, fragment_shader_source, NULL);
		glCompileShader(fragment_shader);

		//create program,attach shader to it, and link it
		program = glCreateProgram(); //glCreateProgram 創建一個程式物件，我們可將著色器物件附加到該物件上
		glAttachShader(program, vertex_shader); //glAttachShader 將一個著色器物件附加到一個程式物件中
		glAttachShader(program, fragment_shader);
		glLinkProgram(program); //將所有附加到程式物件的著色器物件鏈接在一起

		//delete the shader as the program has them now
		//洗掉著色器物件的原因是：一旦著色器鏈接到一個程式物件，程式將包含二進制代碼，并不在需要著色器
		glDeleteShader(vertex_shader);
		glDeleteShader(fragment_shader);

		glPointSize(40.0f);
		return program;

	}

private:
	GLuint rendering_program;
	GLuint vertex_array_object;

};

運行結果：

未完待續