OpenGL Shading Language (2)

Posted on 2017/06/04, 11:56 AM By admin22

前回のWebGLではなく、OpenGL3.3を使って今度は3D表示をしてみました。3Dになるとカメラ位置の計算で行列演算が入り、急に数学的な手法が多用されるようになります。

参考 : http://www.opengl-tutorial.org/jp/beginners-tutorials/tutorial-3-matrices/

ここにあるチュートリアルを参考にさせていただきました。
Windowsでのビルドがうまくいったので、VisualStudio 2013 でテストしました。

参考 : http://www.opengl-tutorial.org/jp/beginners-tutorials/tutorial-1-opening-a-window/

内容は、四面体の頂点の色をフラグメンシェーダに処理をさせることと、座標変換による見え方の違いを確認することです。

// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <glfw3.h>
GLFWwindow* window;

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;

#include <common/shader.hpp>

int main( void )
{
        // Initialise GLFW
	glfwInit();

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); 
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); 

	window = glfwCreateWindow(640, 480, "Test", NULL, NULL);

	glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile

	glewInit();

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "vertexshader.glsl", "fragmentshader.glsl" );

	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");

	// Projection matrix : 45ｰ Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
	glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
	
	// Camera matrix
	glm::mat4 View       = glm::lookAt(
								glm::vec3(0.5,0.8,2), // Camera is at (4,3,3), in World Space
								glm::vec3(0,0,0), // and looks at the origin
								glm::vec3(0,1,0)  // Head is up (set to 0,-1,0 to look upside-down)
						   );
	// Model matrix : an identity matrix (model will be at the origin)
	glm::mat4 Model      = glm::mat4(1.0f);
	// Our ModelViewProjection : multiplication of our 3 matrices
	glm::mat4 MVP        = Projection * View * Model; // Remember, matrix multiplication is the other way around

	static const GLfloat g_vertex_buffer_data[] = { 
		-1.0f, -1.0f, 0.0f, //1
		 1.0f, -1.0f, 0.0f, //2
		 0.0f,  1.0f, 0.0f, //3

		-1.0f, -1.0f, 0.0f,  //1
		 1.0f, -1.0f, 0.0f,  //2
		 0.0f,  0.0f, 1.0f,  //4

		-1.0f, -1.0f, 0.0f,  //1
		 0.0f,  0.0f, 1.0f,  //4
		 0.0f,  1.0f, 0.0f,  //3

		 1.0f, -1.0f, 0.0f,  //2
		 0.0f,  1.0f, 0.0f,  //3
		 0.0f,  0.0f, 1.0f,  //4
	};

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

	static const GLfloat g_color_buffer_data[] = {
		1.0f, 0.0f, 0.0f,
		0.0f, 1.0f, 0.0f,
		0.0f, 0.0f, 1.0f,

		1.0f, 0.0f, 0.0f,
		0.0f, 1.0f, 0.0f,
		1.0f, 1.0f, 1.0f,

		1.0f, 0.0f, 0.0f,
		1.0f, 1.0f, 1.0f,
		0.0f, 0.0f, 1.0f,

		0.0f, 1.0f, 0.0f,
		0.0f, 0.0f, 1.0f,
		1.0f, 1.0f, 1.0f,
	};

	GLuint colorbuffer;
	glGenBuffers(1, &colorbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);

	do{
		// Clear the screen
		glClear( GL_COLOR_BUFFER_BIT );

		// Use our shader
		glUseProgram(programID);

		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		// 2nd attribute buffer : colors
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
		glVertexAttribPointer(
			1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
			3,                                // size
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 3*4); // 3 indices starting at 0 -> 1 triangle
		glDisableVertexAttribArray(0);

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );

	// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteProgram(programID);
	glDeleteVertexArrays(1, &VertexArrayID);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

// Include standard headers

#include <stdio.h>

#include <stdlib.h>

#include <GL/glew.h>

#include <glfw3.h>

GLFWwindow* window;

#include <glm/glm.hpp>

#include <glm/gtc/matrix_transform.hpp>

using namespace glm;

#include <common/shader.hpp>

int main( void )

{

// Initialise GLFW

glfwInit();

glfwWindowHint(GLFW_SAMPLES, 4);

glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);

glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);

glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

window = glfwCreateWindow(640, 480, "Test", NULL, NULL);

glfwMakeContextCurrent(window);

// Initialize GLEW

glewExperimental = true; // Needed for core profile

glewInit();

// Ensure we can capture the escape key being pressed below

glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

// Dark blue background

glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

GLuint VertexArrayID;

glGenVertexArrays(1, &VertexArrayID);

glBindVertexArray(VertexArrayID);

// Create and compile our GLSL program from the shaders

GLuint programID = LoadShaders( "vertexshader.glsl", "fragmentshader.glsl" );

// Get a handle for our "MVP" uniform

GLuint MatrixID = glGetUniformLocation(programID, "MVP");

// Projection matrix : 45ｰ Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units

glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);

// Camera matrix

glm::mat4 View = glm::lookAt(

glm::vec3(0.5,0.8,2), // Camera is at (4,3,3), in World Space

glm::vec3(0,0,0), // and looks at the origin

glm::vec3(0,1,0) // Head is up (set to 0,-1,0 to look upside-down)

);

// Model matrix : an identity matrix (model will be at the origin)

glm::mat4 Model = glm::mat4(1.0f);

// Our ModelViewProjection : multiplication of our 3 matrices

glm::mat4 MVP = Projection * View * Model; // Remember, matrix multiplication is the other way around

static const GLfloat g_vertex_buffer_data[] = {

-1.0f, -1.0f, 0.0f, //1

1.0f, -1.0f, 0.0f, //2

0.0f, 1.0f, 0.0f, //3

-1.0f, -1.0f, 0.0f, //1

1.0f, -1.0f, 0.0f, //2

0.0f, 0.0f, 1.0f, //4

-1.0f, -1.0f, 0.0f, //1

0.0f, 0.0f, 1.0f, //4

0.0f, 1.0f, 0.0f, //3

1.0f, -1.0f, 0.0f, //2

0.0f, 1.0f, 0.0f, //3

0.0f, 0.0f, 1.0f, //4

};

GLuint vertexbuffer;

glGenBuffers(1, &vertexbuffer);

glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);

glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

static const GLfloat g_color_buffer_data[] = {

1.0f, 0.0f, 0.0f,

0.0f, 1.0f, 0.0f,

0.0f, 0.0f, 1.0f,

1.0f, 0.0f, 0.0f,

0.0f, 1.0f, 0.0f,

1.0f, 1.0f, 1.0f,

1.0f, 0.0f, 0.0f,

1.0f, 1.0f, 1.0f,

0.0f, 0.0f, 1.0f,

0.0f, 1.0f, 0.0f,

0.0f, 0.0f, 1.0f,

1.0f, 1.0f, 1.0f,

};

GLuint colorbuffer;

glGenBuffers(1, &colorbuffer);

glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);

glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);

do{

// Clear the screen

glClear( GL_COLOR_BUFFER_BIT );

// Use our shader

glUseProgram(programID);

// Send our transformation to the currently bound shader,

// in the "MVP" uniform

glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

// 1rst attribute buffer : vertices

glEnableVertexAttribArray(0);

glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);

glVertexAttribPointer(

0, // attribute. No particular reason for 0, but must match the layout in the shader.

3, // size

GL_FLOAT, // type

GL_FALSE, // normalized?

0, // stride

(void*)0 // array buffer offset

);

// 2nd attribute buffer : colors

glEnableVertexAttribArray(1);

glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);

glVertexAttribPointer(

1, // attribute. No particular reason for 1, but must match the layout in the shader.

3, // size

GL_FLOAT, // type

GL_FALSE, // normalized?

0, // stride

(void*)0 // array buffer offset

);

// Draw the triangle !

glDrawArrays(GL_TRIANGLES, 0, 3*4); // 3 indices starting at 0 -> 1 triangle

glDisableVertexAttribArray(0);

// Swap buffers

glfwSwapBuffers(window);

glfwPollEvents();

} // Check if the ESC key was pressed or the window was closed

while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&

glfwWindowShouldClose(window) == 0 );

// Cleanup VBO and shader

glDeleteBuffers(1, &vertexbuffer);

glDeleteProgram(programID);

glDeleteVertexArrays(1, &VertexArrayID);

// Close OpenGL window and terminate GLFW

glfwTerminate();

return 0;

}

今回はGLSLがシンプルです。バージョンがかわりattributeのかわりにinが使われるようになりましたが、基本的な文法は同じです。

バーテックスシェーダ

#version 330 core

layout(location = 0) in vec3 vPosition;
layout(location = 1) in vec3 vColor;
uniform mat4 MVP;
out vec3 fColor;

void main(){
	gl_Position =  MVP * vec4(vPosition,1);
	//gl_Position =  vec4(vPosition,1);

	fColor = vColor;
}

#version 330 core

layout(location = 0) in vec3 vPosition;

layout(location = 1) in vec3 vColor;

uniform mat4 MVP;

out vec3 fColor;

void main(){

gl_Position = MVP * vec4(vPosition,1);

//gl_Position = vec4(vPosition,1);

fColor = vColor;

}

フラグメントシェーダ

#version 330 core

in vec3 fColor;
out vec3 color;

void main()
{
	//color = vec3(1,0,0);
	color = fColor;
}

#version 330 core

in vec3 fColor;

out vec3 color;

void main()

{

//color = vec3(1,0,0);

color = fColor;

}

バーテックスが持っている色情報をフラグメントにわたしています。自動的に中間値が計算され補間されます。(GPUが全部やってくれる)
シェーダ部分は別ファイルになっていて、これを読み込んで設定する関数が用意されています。
四面体をカメラ座標の変換をするものとしないもの両方出力してみました。(切り替えはバーテックスシェーダのコメントで)

座標変換なし

座標変換あり

とても基本的なテストですが、VisualStudioでセットアップできたことが、自分の開発環境的に有意義でした。(Compute Shaderに備えて・・)
頂点増やしたり、いろいろと数値を変えて試してみると理解も深まります。

About admin22

Categories: Graphics タグ: GLSL

About admin22

Recent Posts

Tag

Links

Archive