opengl 学习 之 06 lesson

opengl 学习 之 06 lesson

简介

随着键盘和鼠标来控制显示效果。

link

http://www.opengl-tutorial.org/uncategorized/2017/06/07/website-update/

Q&A

1. 已知球坐标系的三个两个角度和长度如果求其方向向量

   // Direction : Spherical coordinates to Cartesian coordinates conversion
   glm::vec3 direction(
    cos(verticalAngle) * sin(horizontalAngle),
    sin(verticalAngle),
    cos(verticalAngle) * cos(horizontalAngle)
   );
   

   参考链接 https://jingyan.baidu.com/article/948f5924f37340d80ff5f93d.html

2. 知道了水平的方向向量如何求逆时针旋转\(\pi /2\)的向量。

   参考链接 https://linux.die.net/man/3/glmatrixmode

   其实想象一个单位圆，然后一个向量旋转了一定的角度。

   // Right vector
   glm::vec3 right = glm::vec3(
    sin(horizontalAngle - 3.14f/2.0f),
    0,
    cos(horizontalAngle - 3.14f/2.0f)
   );
   

TIPS

可以做到将三角面片的法向量如果不是朝向摄像机的话删去

*// Cull triangles which normal is not towards the camera

glEnable(GL_CULL_FACE);

这个实例在linux上执行不成功一直在闪烁就是动的很快，不知道。

其中按键移动上下左右改变摄像机的坐标。

鼠标改变摄像机的朝向

code

// Include GLFW
#include <GLFW/glfw3.h>
extern GLFWwindow* window; // The "extern" keyword here is to access the variable "window" declared in tutorialXXX.cpp. This is a hack to keep the tutorials simple. Please avoid this.

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

#include "controls.hpp"

glm::mat4 ViewMatrix;
glm::mat4 ProjectionMatrix;

glm::mat4 getViewMatrix(){
	return ViewMatrix;
}
glm::mat4 getProjectionMatrix(){
	return ProjectionMatrix;
}

// Initial position : on +Z
glm::vec3 position = glm::vec3( 0, 0, 5 );
// Initial horizontal angle : toward -Z
float horizontalAngle = 3.14f;
// Initial vertical angle : none
float verticalAngle = 0.0f;
// Initial Field of View
float initialFoV = 45.0f;

float speed = 3.0f; // 3 units / second
float mouseSpeed = 0.005f;

void computeMatricesFromInputs(){

	// glfwGetTime is called only once, the first time this function is called
	static double lastTime = glfwGetTime();

	// Compute time difference between current and last frame
	double currentTime = glfwGetTime();
	float deltaTime = float(currentTime - lastTime);

	// Get mouse position
	double xpos, ypos;
	glfwGetCursorPos(window, &xpos, &ypos);

	// Reset mouse position for next frame
	glfwSetCursorPos(window, 1024/2, 768/2);

	// Compute new orientation
	horizontalAngle += mouseSpeed * float(1024/2 - xpos );
	verticalAngle   += mouseSpeed * float( 768/2 - ypos );

	// Direction : Spherical coordinates to Cartesian coordinates conversion
	glm::vec3 direction(
		cos(verticalAngle) * sin(horizontalAngle),
		sin(verticalAngle),
		cos(verticalAngle) * cos(horizontalAngle)
	);

	// Right vector
	glm::vec3 right = glm::vec3(
		sin(horizontalAngle - 3.14f/2.0f),
		0,
		cos(horizontalAngle - 3.14f/2.0f)
	);

	// Up vector
	glm::vec3 up = glm::cross( right, direction );

	// Move forward
	if (glfwGetKey( window, GLFW_KEY_UP ) == GLFW_PRESS){
		position += direction * deltaTime * speed;
	}
	// Move backward
	if (glfwGetKey( window, GLFW_KEY_DOWN ) == GLFW_PRESS){
		position -= direction * deltaTime * speed;
	}
	// Strafe right
	if (glfwGetKey( window, GLFW_KEY_RIGHT ) == GLFW_PRESS){
		position += right * deltaTime * speed;
	}
	// Strafe left
	if (glfwGetKey( window, GLFW_KEY_LEFT ) == GLFW_PRESS){
		position -= right * deltaTime * speed;
	}

	float FoV = initialFoV;// - 5 * glfwGetMouseWheel(); // Now GLFW 3 requires setting up a callback for this. It's a bit too complicated for this beginner's tutorial, so it's disabled instead.

	// Projection matrix : 45� Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
	ProjectionMatrix = glm::perspective(glm::radians(FoV), 4.0f / 3.0f, 0.1f, 100.0f);
	// Camera matrix
	ViewMatrix       = glm::lookAt(
								position,           // Camera is here
								position+direction, // and looks here : at the same position, plus "direction"
								up                  // Head is up (set to 0,-1,0 to look upside-down)
						   );

	// For the next frame, the "last time" will be "now"
	lastTime = currentTime;
}

#ifndef CONTROLS_HPP
#define CONTROLS_HPP

void computeMatricesFromInputs();
glm::mat4 getViewMatrix();
glm::mat4 getProjectionMatrix();

#endif

// Include standard headers
#include <stdio.h>
#include <stdlib.h>

// Include GLEW
#include <GL/glew.h>

// Include GLFW
#include <GLFW/glfw3.h>
GLFWwindow* window;

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

#include <common/shader.hpp>
#include <common/texture.hpp>
#include <common/controls.hpp>

int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW\n" );
		getchar();
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Tutorial 0 - Keyboard and Mouse", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" );
		getchar();
		glfwTerminate();
		return -1;
	}
    glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW\n");
		getchar();
		glfwTerminate();
		return -1;
	}

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    // Hide the mouse and enable unlimited mouvement
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    // Set the mouse at the center of the screen
    glfwPollEvents();
    glfwSetCursorPos(window, 1024/2, 768/2);

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

	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it closer to the camera than the former one
	glDepthFunc(GL_LESS); 

	// Cull triangles which normal is not towards the camera
	glEnable(GL_CULL_FACE);

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

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

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

	// Load the texture
	GLuint Texture = loadDDS("uvtemplate.DDS");

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

	// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
	// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
	static const GLfloat g_vertex_buffer_data[] = {
		-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,-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, 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,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f
	};

	// Two UV coordinatesfor each vertex. They were created with Blender.
	static const GLfloat g_uv_buffer_data[] = {
		0.000059f, 0.000004f,
		0.000103f, 0.336048f,
		0.335973f, 0.335903f,
		1.000023f, 0.000013f,
		0.667979f, 0.335851f,
		0.999958f, 0.336064f,
		0.667979f, 0.335851f,
		0.336024f, 0.671877f,
		0.667969f, 0.671889f,
		1.000023f, 0.000013f,
		0.668104f, 0.000013f,
		0.667979f, 0.335851f,
		0.000059f, 0.000004f,
		0.335973f, 0.335903f,
		0.336098f, 0.000071f,
		0.667979f, 0.335851f,
		0.335973f, 0.335903f,
		0.336024f, 0.671877f,
		1.000004f, 0.671847f,
		0.999958f, 0.336064f,
		0.667979f, 0.335851f,
		0.668104f, 0.000013f,
		0.335973f, 0.335903f,
		0.667979f, 0.335851f,
		0.335973f, 0.335903f,
		0.668104f, 0.000013f,
		0.336098f, 0.000071f,
		0.000103f, 0.336048f,
		0.000004f, 0.671870f,
		0.336024f, 0.671877f,
		0.000103f, 0.336048f,
		0.336024f, 0.671877f,
		0.335973f, 0.335903f,
		0.667969f, 0.671889f,
		1.000004f, 0.671847f,
		0.667979f, 0.335851f
	};

	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);

	GLuint uvbuffer;
	glGenBuffers(1, &uvbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_uv_buffer_data), g_uv_buffer_data, GL_STATIC_DRAW);

	do{

		// Clear the screen
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(programID);

		// Compute the MVP matrix from keyboard and mouse input
		computeMatricesFromInputs();
		glm::mat4 ProjectionMatrix = getProjectionMatrix();
		glm::mat4 ViewMatrix = getViewMatrix();
		glm::mat4 ModelMatrix = glm::mat4(1.0);
		glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;

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

		// Bind our texture in Texture Unit 0
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, Texture);
		// Set our "myTextureSampler" sampler to use Texture Unit 0
		glUniform1i(TextureID, 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 : UVs
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
		glVertexAttribPointer(
			1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
			2,                                // size : U+V => 2
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

		// 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);
	glDeleteBuffers(1, &uvbuffer);
	glDeleteProgram(programID);
	glDeleteTextures(1, &TextureID);
	glDeleteVertexArrays(1, &VertexArrayID);

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

	return 0;
}

#version 330 core

// Input vertex data, different for all executions of this shader.
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec2 vertexUV;

// Output data ; will be interpolated for each fragment.
out vec2 UV;

// Values that stay constant for the whole mesh.
uniform mat4 MVP;

void main(){

	// Output position of the vertex, in clip space : MVP * position
	gl_Position =  MVP * vec4(vertexPosition_modelspace,1);

	// UV of the vertex. No special space for this one.
	UV = vertexUV;
}

#version 330 core

// Interpolated values from the vertex shaders
in vec2 UV;

// Ouput data
out vec3 color;

// Values that stay constant for the whole mesh.
uniform sampler2D myTextureSampler;

void main(){

	// Output color = color of the texture at the specified UV
	color = texture( myTextureSampler, UV ).rgb;
}