[C++知识库]C++/OpenGL 入门(10):实例化24个/10万个立方体同时运动

1. 来源：《Computer Graphics Programming in OpenGL Using C++ 》by V Scott Gordon John L Clevenger
2. 内容：程序4.2 Instancing – Twenty-Four Animated Cubes，书P80页，PDF99/403
3. 相关介绍可参考OpenGL–用一个立方体实例化为10万个立方体
4. 这里参考了OpenGL–用一个立方体实例化为10万个立方体的 vertShader.glsl 和 fragShader.glsl 两份文件
   结果，生成多个转动的彩色立方体，如下

生成24个立方体同时运动

1. 文件1： 4.2 instancing.cpp

#include <string>
#include <iostream>
#include <fstream>
#include <cmath>


#include "glm\glm.hpp"
#include "glm\gtc\type_ptr.hpp"
#include "glm\gtc\matrix_transform.hpp"
#include "Utils\4.1 Utils.h"
using namespace std;
#define numVAOs 1
#define numVBOs 2
float cameraX, cameraY, cameraZ;
float cubeLocX, cubeLocY, cubeLocZ;
GLuint renderingProgram;
GLuint vao[numVAOs];
GLuint vbo[numVBOs];

// allocate variables used in display() function, 
// so that they won’t need to be allocated during rendering
GLuint mvLoc, projLoc,vLoc,tfLoc;
int width, height;
float aspect, timeFactor;
glm::mat4 pMat, vMat, mMat, mvMat;
glm::mat4 tMat, rMat;//为了动画而添加的内容

void setupVertices(void) {
	// 36 vertices, 12 triangles, makes 2x2x2 cube placed at origin
	float vertexPositions[108] = {
	 -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
	};
	glGenVertexArrays(1, vao);
	glBindVertexArray(vao[0]);
	glGenBuffers(numVBOs, vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);
}
void init(GLFWwindow* window) {

	//renderingProgram = createShaderProgram("add/4.1 vertShader.glsl", "add/4.1 fragShader.glsl");
	renderingProgram = createShaderProgram("add/4.2 vertShader.glsl", "add/4.2 fragShader.glsl");
	cameraX = 0.0f; cameraY = 0.0f; cameraZ = 32.0f;//24个立方体对应z=32，10万个对应420
	//cubeLocX = 0.0f; cubeLocY = -2.0f; cubeLocZ = 0.0f; // shift down Y to reveal perspective
	setupVertices();
}

void display(GLFWwindow* window, double currentTime) {
	glClear(GL_DEPTH_BUFFER_BIT);
	glClearColor(0.0, 0.0, 0.0, 1.0);
	glClear(GL_COLOR_BUFFER_BIT); // 每一次都将背景清理（clear）为黑色
	glUseProgram(renderingProgram);
	// get the uniform variables for the MV and projection matrices
	vLoc = glGetUniformLocation(renderingProgram, "v_matrix");
	projLoc = glGetUniformLocation(renderingProgram, "proj_matrix");
	vMat = glm::translate(glm::mat4(1.0f), glm::vec3(-cameraX, -cameraY, -cameraZ));
	// build perspective matrix
	glfwGetFramebufferSize(window, &width, &height);
	aspect = (float)width / (float)height;
	pMat = glm::perspective(1.0472f, aspect, 0.1f, 1000.0f); // 1.0472 radians = 60 degrees
	glUniformMatrix4fv(vLoc, 1, GL_FALSE, glm::value_ptr(vMat)); // shader needs the V matrix
	glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(pMat));
															 // build view matrix, model matrix, and model-view matrix

	timeFactor = ((float)currentTime); // uniform for the time factor
	tfLoc = glGetUniformLocation(renderingProgram, "tf"); // (the shader needs that too)
	glUniform1f(tfLoc, (float)timeFactor);

	// associate VBO with the corresponding vertex attribute in the vertex shader
	glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
	glEnableVertexAttribArray(0);
	// adjust OpenGL settings and draw model
	glEnable(GL_DEPTH_TEST);
	glDepthFunc(GL_LEQUAL);
	glDrawArraysInstanced(GL_TRIANGLES, 0, 36, 24);// 24---24个立方体，100000---10万个立方体
}

int main(void) { // main() is unchanged from before
	if (!glfwInit()) { exit(EXIT_FAILURE); }
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	GLFWwindow* window = glfwCreateWindow(600, 600, "Chapter 4 - program 1", NULL, NULL);
	glfwMakeContextCurrent(window);
	if (glewInit() != GLEW_OK) { exit(EXIT_FAILURE); }
	glfwSwapInterval(1);
	init(window);
	while (!glfwWindowShouldClose(window)) {
		display(window, glfwGetTime());
		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glfwDestroyWindow(window);
	glfwTerminate();
	exit(EXIT_SUCCESS);
}

2. 文件2： 4.2 vertShader.glsl 参考OpenGL–用一个立方体实例化为10万个立方体的即可运行

#version 430

layout (location=0) in vec3 position;

uniform mat4 v_matrix;
uniform mat4 proj_matrix;
uniform float tf;//用于动画和放置立方体的时间因子

out vec4 varyingColor;

mat4 buildRotateX(float rad);//矩阵变换工具函数的声明
mat4 buildRotateY(float rad);//glsl要求函数先声明后调用
mat4 buildRotateZ(float rad);
mat4 buildTranslate(float x,float y,float z);

void main(void)
{
	float i=gl_InstanceID+tf; //取值基于时间因子，但是对每个立方体示例也都不同的。

	float a=sin(0.35*i)*8.0; //这些是用来平移的x,y,z分量,24个的时候
	float b=sin(0.52*i)*8.0;
	float c=sin(0.70*i)*8.0;

	//float a=sin(203.0*i/8000.0)*403.0; //这些是用来平移的x,y,z分量
	//float b=sin(301.0*i/4001.0)*401.0;
	//float c=sin(400.0*i/6003.0)*405.0;

	//构建旋转和平移矩阵，将会应用于当前立方体的模型矩阵
	mat4 localRotX=buildRotateX(0.1*i);
	mat4 localRotY=buildRotateY(0.1*i);
	mat4 localRotZ=buildRotateZ(0.1*i);
	mat4 localTrans=buildTranslate(a,b,c);

	//构建模型矩阵，然后是模型-视图矩阵
	mat4 newM_matrix=localTrans*localRotX*localRotY*localRotZ;
	mat4 mv_matrix=v_matrix*newM_matrix;
	gl_Position = proj_matrix * mv_matrix * vec4(position,1.0);
	varyingColor = vec4(position,1.0)*0.5+vec4(0.5,0.5,0.5,0.5);
} 

//构建平移矩阵的工具函数（来自第三章）
mat4 buildTranslate(float x,float y,float z)
{
	mat4 trans=mat4(1.0,0.0,0.0,0.0,
	0.0,1.0,0.0,0.0,
	0.0,0.0,1.0,0.0,
	x,y,z,1.0);
	return trans;
}
//用来绕x，y，z轴旋转的类似函数
mat4 buildRotateX(float rad)
{
	mat4 trans=mat4(
	1.0,0.0,0.0,0.0,
	0.0,cos(rad),-sin(rad),0.0,
	0.0,sin(rad),cos(rad),0.0,
	0.0,0.0,0.0,1.0);
	return trans;
}
mat4 buildRotateY(float rad)
{
	mat4 trans=mat4(
	cos(rad),0.0,sin(rad),0.0,
	0.0,1.0,0.0,0.0,
	-sin(rad),0.0,cos(rad),0.0,
	0.0,0.0,0.0,1.0);
	return trans;
}
mat4 buildRotateZ(float rad)
{
	mat4 trans=mat4(
	cos(rad),sin(rad),0.0,0.0,
	-sin(rad),cos(rad),0.0,0.0,
	0.0,0.0,1.0,0.0,
	0.0,0.0,0.0,1.0);
	return trans;
}
3. 文件2： 4.2 fragShader.glsl 参考[OpenGL--用一个立方体实例化为10万个立方体](https://blog.csdn.net/weixin_44210987/article/details/108173586?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522164432910416780271963614%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=164432910416780271963614&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~first_rank_ecpm_v1~rank_v31_ecpm-2-108173586.pc_search_insert_es_download&utm_term=opengl%20%E7%AB%8B%E6%96%B9%E4%BD%93%20%E5%AE%9E%E4%BE%8B%E5%8C%96&spm=1018.2226.3001.4187)的即可运行

```cpp
#version 430

in vec4 varyingColor;
out vec4 color;

uniform mat4 mv_matrix;
uniform mat4 proj_matrix;

void main(void)
{	color = varyingColor;
}

生成10万个立方体同时运动

1. 文件1： 4.2 instancing.cpp

#include <string>
#include <iostream>
#include <fstream>
#include <cmath>


#include "glm\glm.hpp"
#include "glm\gtc\type_ptr.hpp"
#include "glm\gtc\matrix_transform.hpp"
#include "Utils\4.1 Utils.h"
using namespace std;
#define numVAOs 1
#define numVBOs 2
float cameraX, cameraY, cameraZ;
float cubeLocX, cubeLocY, cubeLocZ;
GLuint renderingProgram;
GLuint vao[numVAOs];
GLuint vbo[numVBOs];

// allocate variables used in display() function, 
// so that they won’t need to be allocated during rendering
GLuint mvLoc, projLoc,vLoc,tfLoc;
int width, height;
float aspect, timeFactor;
glm::mat4 pMat, vMat, mMat, mvMat;
glm::mat4 tMat, rMat;//为了动画而添加的内容

void setupVertices(void) {
	// 36 vertices, 12 triangles, makes 2x2x2 cube placed at origin
	float vertexPositions[108] = {
	 -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
	};
	glGenVertexArrays(1, vao);
	glBindVertexArray(vao[0]);
	glGenBuffers(numVBOs, vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);
}
void init(GLFWwindow* window) {

	//renderingProgram = createShaderProgram("add/4.1 vertShader.glsl", "add/4.1 fragShader.glsl");
	renderingProgram = createShaderProgram("add/4.2 vertShader.glsl", "add/4.2 fragShader.glsl");
	cameraX = 0.0f; cameraY = 0.0f; cameraZ = 420.0f;//24个立方体对应z=32，10万个对应420
	//cubeLocX = 0.0f; cubeLocY = -2.0f; cubeLocZ = 0.0f; // shift down Y to reveal perspective
	setupVertices();
}

void display(GLFWwindow* window, double currentTime) {
	glClear(GL_DEPTH_BUFFER_BIT);
	glClearColor(0.0, 0.0, 0.0, 1.0);
	glClear(GL_COLOR_BUFFER_BIT); // 每一次都将背景清理（clear）为黑色
	glUseProgram(renderingProgram);
	// get the uniform variables for the MV and projection matrices
	vLoc = glGetUniformLocation(renderingProgram, "v_matrix");
	projLoc = glGetUniformLocation(renderingProgram, "proj_matrix");
	vMat = glm::translate(glm::mat4(1.0f), glm::vec3(-cameraX, -cameraY, -cameraZ));
	// build perspective matrix
	glfwGetFramebufferSize(window, &width, &height);
	aspect = (float)width / (float)height;
	pMat = glm::perspective(1.0472f, aspect, 0.1f, 1000.0f); // 1.0472 radians = 60 degrees
	glUniformMatrix4fv(vLoc, 1, GL_FALSE, glm::value_ptr(vMat)); // shader needs the V matrix
	glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(pMat));
															 // build view matrix, model matrix, and model-view matrix

	timeFactor = ((float)currentTime); // uniform for the time factor
	tfLoc = glGetUniformLocation(renderingProgram, "tf"); // (the shader needs that too)
	glUniform1f(tfLoc, (float)timeFactor);
	
	// associate VBO with the corresponding vertex attribute in the vertex shader
	glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
	glEnableVertexAttribArray(0);
	// adjust OpenGL settings and draw model
	glEnable(GL_DEPTH_TEST);
	glDepthFunc(GL_LEQUAL);
	glDrawArraysInstanced(GL_TRIANGLES, 0, 36, 100000);// 24个立方体，或改为10万个立方体
}

int main(void) { // main() is unchanged from before
	if (!glfwInit()) { exit(EXIT_FAILURE); }
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	GLFWwindow* window = glfwCreateWindow(600, 600, "Chapter 4 - program 1", NULL, NULL);
	glfwMakeContextCurrent(window);
	if (glewInit() != GLEW_OK) { exit(EXIT_FAILURE); }
	glfwSwapInterval(1);
	init(window);
	while (!glfwWindowShouldClose(window)) {
		display(window, glfwGetTime());
		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glfwDestroyWindow(window);
	glfwTerminate();
	exit(EXIT_SUCCESS);
}

2. 文件2： 4.2 vertShader.glsl 参考OpenGL–用一个立方体实例化为10万个立方体的即可运行

#version 430

layout (location=0) in vec3 position;

uniform mat4 v_matrix;
uniform mat4 proj_matrix;
uniform float tf;//用于动画和放置立方体的时间因子

out vec4 varyingColor;

mat4 buildRotateX(float rad);//矩阵变换工具函数的声明
mat4 buildRotateY(float rad);//glsl要求函数先声明后调用
mat4 buildRotateZ(float rad);
mat4 buildTranslate(float x,float y,float z);

void main(void)
{
	float i=gl_InstanceID+tf; //取值基于时间因子，但是对每个立方体示例也都不同的。

	//float a=sin(0.35*i)*8.0; //这些是用来平移的x,y,z分量,24个的时候
	//float b=sin(0.52*i)*8.0;
	//float c=sin(0.70*i)*8.0;

	float a=sin(203.0*i/8000.0)*403.0; //这些是用来平移的x,y,z分量
	float b=sin(301.0*i/4001.0)*401.0;
	float c=sin(400.0*i/6003.0)*405.0;

	//构建旋转和平移矩阵，将会应用于当前立方体的模型矩阵
	mat4 localRotX=buildRotateX(0.1*i);
	mat4 localRotY=buildRotateY(0.1*i);
	mat4 localRotZ=buildRotateZ(0.1*i);
	mat4 localTrans=buildTranslate(a,b,c);

	//构建模型矩阵，然后是模型-视图矩阵
	mat4 newM_matrix=localTrans*localRotX*localRotY*localRotZ;
	mat4 mv_matrix=v_matrix*newM_matrix;
	gl_Position = proj_matrix * mv_matrix * vec4(position,1.0);
	varyingColor = vec4(position,1.0)*0.5+vec4(0.5,0.5,0.5,0.5);
} 

//构建平移矩阵的工具函数（来自第三章）
mat4 buildTranslate(float x,float y,float z)
{
	mat4 trans=mat4(1.0,0.0,0.0,0.0,
	0.0,1.0,0.0,0.0,
	0.0,0.0,1.0,0.0,
	x,y,z,1.0);
	return trans;
}
//用来绕x，y，z轴旋转的类似函数
mat4 buildRotateX(float rad)
{
	mat4 trans=mat4(
	1.0,0.0,0.0,0.0,
	0.0,cos(rad),-sin(rad),0.0,
	0.0,sin(rad),cos(rad),0.0,
	0.0,0.0,0.0,1.0);
	return trans;
}
mat4 buildRotateY(float rad)
{
	mat4 trans=mat4(
	cos(rad),0.0,sin(rad),0.0,
	0.0,1.0,0.0,0.0,
	-sin(rad),0.0,cos(rad),0.0,
	0.0,0.0,0.0,1.0);
	return trans;
}
mat4 buildRotateZ(float rad)
{
	mat4 trans=mat4(
	cos(rad),sin(rad),0.0,0.0,
	-sin(rad),cos(rad),0.0,0.0,
	0.0,0.0,1.0,0.0,
	0.0,0.0,0.0,1.0);
	return trans;
}

3. 文件2： 4.2 fragShader.glsl 参考OpenGL–用一个立方体实例化为10万个立方体的即可运行 (与生成24个立方体的相同，无需修改)

#version 430

in vec4 varyingColor;
out vec4 color;

uniform mat4 mv_matrix;
uniform mat4 proj_matrix;

void main(void)
{	color = varyingColor;
}

改变立方体的数量，需要更改的部分

1. 4.2 instancing.cpp中，主要改两个地方
   init 函数：
   cameraX = 0.0f; cameraY = 0.0f; cameraZ = 32.0f; //24个立方体时对应z=32
   cameraX = 0.0f; cameraY = 0.0f; cameraZ = 420.0f; //10万个立方体时对应z=420
   display 函数：
   glDrawArraysInstanced(GL_TRIANGLES, 0, 36, 24); // 24个立方体，
   glDrawArraysInstanced(GL_TRIANGLES, 0, 36, 100000); // 10万个立方体

2. 4.2 vertShader.glsl
   如果是10万个立方体：
   //float a=sin(0.35*i)8.0; //这些是用来平移的x,y,z分量,24个的时候
   //float b=sin(0.52i)8.0;
   //float c=sin(0.70i)*8.0;

float a=sin(203.0*i/8000.0)*403.0; //这些是用来平移的x,y,z分量
float b=sin(301.0*i/4001.0)*401.0;
float c=sin(400.0*i/6003.0)*405.0;

如果是24个立方体：
float a=sin(0.35*i)8.0; //这些是用来平移的x,y,z分量,24个的时候
float b=sin(0.52i)8.0;
float c=sin(0.70i)*8.0;

//float a=sin(203.0*i/8000.0)*403.0; //这些是用来平移的x,y,z分量
//float b=sin(301.0*i/4001.0)*401.0;
//float c=sin(400.0*i/6003.0)*405.0;

3. 4.2 fragShader.glsl文件中不需要更改