如何在OpenGL中结合纹理和照明
我正在尝试在OpenGL中结合金字塔上的纹理和照明。我基本上是从合并两个独立的代码开始的，现在，我正在努力进行更改以平滑合并。然而，我有两个问题如何在OpenGL中结合纹理和照明,opengl,texture-mapping,lighting,Opengl,Texture Mapping,Lighting,我正在尝试在OpenGL中结合金字塔上的纹理和照明。我基本上是从合并两个独立的代码开始的，现在，我正在努力进行更改以平滑合并。然而，我有两个问题 我需要删除对象颜色并用纹理替换它，但我不确定如何用这段代码解决这个问题，因为对象颜色在代码中根深蒂固 我不知道如何列出位置、法线和纹理的坐标。他们目前的安排似乎给产出带来了很多问题 对于第一个问题，我尝试用纹理替换pyramidColor和objectColor，但它似乎产生了更多问题 对于第二个问题，我尝试将列表顺序重新排列为位置、纹理和法线，这对一
/*Header Inclusions*/
#include <iostream>
#include <GL/glew.h>
#include <GL/freeglut.h>
//GLM Math Header Inclusions
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
//SOIL image loader Inclusion
#include "SOIL2/SOIL2.h"
using namespace std; //Standard namespace
#define WINDOW_TITLE "Pyramid" //Window title Macro
/*Shader program Macro*/
#ifndef GLSL
#define GLSL(Version, Source) "#version " #Version "\n" #Source
#endif
/*Variable declarations for shader, window size initialization, buffer and array objects */
GLint pyramidShaderProgram, lampShaderProgram, WindowWidth = 800, WindowHeight = 600;
GLuint VBO, PyramidVAO, LightVAO, texture;
//Subject position and scale
glm::vec3 pyramidPosition(0.0f, 0.0f, 0.0f);
glm::vec3 pyramidScale(2.0f);
//pyramid and light color
glm::vec3 objectColor(1.0f, 1.0f, 1.0f);
glm::vec3 lightColor(1.0f, 1.0f, 1.0f);
//Light position and scale
glm::vec3 lightPosition(0.5f, 0.5f, -3.0f);
glm::vec3 lightScale(0.3f);
//Camera position
glm::vec3 cameraPosition(0.0f, 0.0f, -6.0f);
//Camera rotation
float cameraRotation = glm::radians(-25.0f);
/*Function prototypes*/
void UResizeWindow(int, int);
void URenderGraphics(void);
void UCreateShader(void);
void UCreateBuffers(void);
void UGenerateTexture(void);
/*Pyramid Vertex Shader Source Code*/
const GLchar * pyramidVertexShaderSource = GLSL(330,
layout (location = 0) in vec3 position; //Vertex data from Vertex Attrib Pointer 0
layout (location = 1) in vec3 normal; //VAP position 1 for normals
layout (location = 2) in vec2 textureCoordinate;
out vec3 FragmentPos; //For outgoing color / pixels to fragment shader
out vec3 Normal; //For outgoing normals to fragment shader
out vec2 mobileTextureCoordinate;
//Global variables for the transform matrices
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
void main(){
gl_Position = projection * view * model * vec4(position, 1.0f); //transforms vertices to clip coordinates
FragmentPos = vec3(model * vec4(position, 1.0f)); //Gets fragment / pixel position in world space only (exclude view and projection)
Normal = mat3(transpose(inverse(model))) * normal; //get normal vectors in world space only and exclude normal translation properties
mobileTextureCoordinate = vec2(textureCoordinate.x, 1 - textureCoordinate.y); //flips the texture horizontal
}
);
/*Pyramid Fragment Shader Source Code*/
const GLchar * pyramidFragmentShaderSource = GLSL(330,
in vec3 FragmentPos; //For incoming fragment position
in vec3 Normal; //For incoming normals
in vec2 mobileTextureCoordinate;
out vec4 pyramidColor; //For outgoing pyramid color to the GPU
out vec4 gpuTexture; //Variable to pass color data to the GPU
//Uniform / Global variables for object color, light color, light position, and camera/view position
uniform vec3 objectColor;
uniform vec3 lightColor;
uniform vec3 lightPos;
uniform vec3 viewPosition;
uniform sampler2D uTexture; //Useful when working with multiple textures
void main(){
/*Phong lighting model calculations to generate ambient, diffuse, and specular components*/
//Calculate Ambient Lighting
float ambientStrength = 0.1f; //Set ambient or global lighting strength
vec3 ambient = ambientStrength * lightColor; //Generate ambient light color
//Calculate Diffuse Lighting
vec3 norm = normalize(Normal); //Normalize vectors to 1 unit
vec3 lightDirection = normalize(lightPos - FragmentPos); //Calculate distance (light direction) between light source and fragments/pixels on
float impact = max(dot(norm, lightDirection), 0.0); //Calculate diffuse impact by generating dot product of normal and light
vec3 diffuse = impact * lightColor; //Generate diffuse light color
//Calculate Specular lighting
float specularIntensity = 0.8f; //Set specular light strength
float highlightSize = 128.0f; //Set specular highlight size
vec3 viewDir = normalize(viewPosition - FragmentPos); //Calculate view direction
vec3 reflectDir = reflect(-lightDirection, norm); //Calculate reflection vector
//Calculate specular component
float specularComponent = pow(max(dot(viewDir, reflectDir), 0.0), highlightSize);
vec3 specular = specularIntensity * specularComponent * lightColor;
//Calculate phong result
vec3 phong = (ambient + diffuse + specular) * objectColor;
pyramidColor = vec4(phong, 1.0f); //Send lighting results to GPU
gpuTexture = texture(uTexture, mobileTextureCoordinate);
}
);
/*Lamp Shader Source Code*/
const GLchar * lampVertexShaderSource = GLSL(330,
layout (location = 0) in vec3 position; //VAP position 0 for vertex position data
//Uniform / Global variables for the transform matrices
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
void main()
{
gl_Position = projection * view *model * vec4(position, 1.0f); //Transforms vertices into clip coordinates
}
);
/*Fragment Shader Source Code*/
const GLchar * lampFragmentShaderSource = GLSL(330,
out vec4 color; //For outgoing lamp color (smaller pyramid) to the GPU
void main()
{
color = vec4(1.0f); //Set color to white (1.0f, 1.0f, 1.0f) with alpha 1.0
}
);
/*Main Program*/
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowSize(WindowWidth, WindowHeight);
glutCreateWindow(WINDOW_TITLE);
glutReshapeFunc(UResizeWindow);
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK)
{
std::cout<< "Failed to initialize GLEW" << std::endl;
return -1;
}
UCreateShader();
UCreateBuffers();
UGenerateTexture();
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); //Set background color
glutDisplayFunc(URenderGraphics);
glutMainLoop();
//Destroys Buffer objects once used
glDeleteVertexArrays(1, &PyramidVAO);
glDeleteVertexArrays(1, &LightVAO);
glDeleteBuffers(1, &VBO);
return 0;
}
/*Resizes the window*/
void UResizeWindow(int w, int h)
{
WindowWidth = w;
WindowHeight = h;
glViewport(0, 0, WindowWidth, WindowHeight);
}
/*Renders graphics*/
void URenderGraphics(void)
{
glEnable(GL_DEPTH_TEST); //Enable z-depth
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Clears the screen
GLint modelLoc, viewLoc, projLoc, objectColorLoc, lightColorLoc, lightPositionLoc, viewPositionLoc;
glm::mat4 model;
glm::mat4 view;
glm::mat4 projection;
/*********Use the pyramid Shader to activate the pyramid Vertex Array Object for rendering and transforming*********/
glUseProgram(pyramidShaderProgram);
glBindVertexArray(PyramidVAO);
//Transform the pyramid
model = glm::translate(model, pyramidPosition);
model = glm::scale(model, pyramidScale);
//Transform the camera
view = glm::translate(view, cameraPosition);
view = glm::rotate(view, cameraRotation, glm::vec3(0.0f, 1.0f, 0.0f));
//Set the camera projection to perspective
projection = glm::perspective(45.0f,(GLfloat)WindowWidth / (GLfloat)WindowHeight, 0.1f, 100.0f);
//Reference matrix uniforms from the pyramid Shader program
modelLoc = glGetUniformLocation(pyramidShaderProgram, "model");
viewLoc = glGetUniformLocation(pyramidShaderProgram, "view");
projLoc = glGetUniformLocation(pyramidShaderProgram, "projection");
//Pass matrix data to the pyramid Shader program's matrix uniforms
glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));
glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(projection));
//Reference matrix uniforms from the pyramid Shader program for the pyramid color, light color, light position, and camera position
objectColorLoc = glGetUniformLocation(pyramidShaderProgram, "objectColor");
lightColorLoc = glGetUniformLocation(pyramidShaderProgram, "lightColor");
lightPositionLoc = glGetUniformLocation(pyramidShaderProgram, "lightPos");
viewPositionLoc = glGetUniformLocation(pyramidShaderProgram, "viewPosition");
//Pass color, light, and camera data to the pyramid Shader programs corresponding uniforms
glUniform3f(objectColorLoc, objectColor.r, objectColor.g, objectColor.b);
glUniform3f(lightColorLoc, lightColor.r, lightColor.g, lightColor.b);
glUniform3f(lightPositionLoc, lightPosition.x, lightPosition.y, lightPosition.z);
glUniform3f(viewPositionLoc, cameraPosition.x, cameraPosition.y, cameraPosition.z);
glDrawArrays(GL_TRIANGLES, 0, 18); //Draw the primitives / pyramid
glBindVertexArray(0); //Deactivate the Pyramid Vertex Array Object
/***************Use the Lamp Shader and activate the Lamp Vertex Array Object for rendering and transforming ************/
glUseProgram(lampShaderProgram);
glBindVertexArray(LightVAO);
//Transform the smaller pyramid used as a visual cue for the light source
model = glm::translate(model, lightPosition);
model = glm::scale(model, lightScale);
//Reference matrix uniforms from the Lamp Shader program
modelLoc = glGetUniformLocation(lampShaderProgram, "model");
viewLoc = glGetUniformLocation(lampShaderProgram, "view");
projLoc = glGetUniformLocation(lampShaderProgram, "projection");
//Pass matrix uniforms from the Lamp Shader Program
glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
glUniformMatrix4fv(viewLoc, 1, GL_FALSE, glm::value_ptr(view));
glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(projection));
glBindTexture(GL_TEXTURE_2D, texture);
//Draws the triangles
glDrawArrays(GL_TRIANGLES, 0, 18);
glBindVertexArray(0); //Deactivate the Lamp Vertex Array Object
glutPostRedisplay();
glutSwapBuffers(); //Flips the back buffer with the front buffer every frame. Similar to GL Flush
}
/*Create the Shader program*/
void UCreateShader()
{
//Pyramid Vertex shader
GLint pyramidVertexShader = glCreateShader(GL_VERTEX_SHADER); //Creates the Vertex shader
glShaderSource(pyramidVertexShader, 1, &pyramidVertexShaderSource, NULL); //Attaches the Vertex shader to the source code
glCompileShader(pyramidVertexShader); //Compiles the Vertex shader
//Pyramid Fragment Shader
GLint pyramidFragmentShader = glCreateShader(GL_FRAGMENT_SHADER); //Creates the Fragment Shader
glShaderSource(pyramidFragmentShader, 1, &pyramidFragmentShaderSource, NULL); //Attaches the Fragment shader to the source code
glCompileShader(pyramidFragmentShader); //Compiles the Fragment Shader
//Pyramid Shader program
pyramidShaderProgram = glCreateProgram(); //Creates the Shader program and returns an id
glAttachShader(pyramidShaderProgram, pyramidVertexShader); //Attaches Vertex shader to the Shader program
glAttachShader(pyramidShaderProgram, pyramidFragmentShader); //Attaches Fragment shader to the Shader program
glLinkProgram(pyramidShaderProgram); //Link Vertex and Fragment shaders to the Shader program
//Delete the Vertex and Fragment shaders once linked
glDeleteShader(pyramidVertexShader);
glDeleteShader(pyramidFragmentShader);
//Lamp Vertex shader
GLint lampVertexShader = glCreateShader(GL_VERTEX_SHADER); //Creates the Vertex shader
glShaderSource(lampVertexShader, 1, &lampVertexShaderSource, NULL); //Attaches the Vertex shader to the source code
glCompileShader(lampVertexShader); //Compiles the Vertex shader
//Lamp Fragment shader
GLint lampFragmentShader = glCreateShader(GL_FRAGMENT_SHADER); //Creates the Fragment shader
glShaderSource(lampFragmentShader, 1, &lampFragmentShaderSource, NULL); //Attaches the Fragment shader to the source code
glCompileShader(lampFragmentShader); //Compiles the Fragment shader
//Lamp Shader Program
lampShaderProgram = glCreateProgram(); //Creates the Shader program and returns an id
glAttachShader(lampShaderProgram, lampVertexShader); //Attach Vertex shader to the Shader program
glAttachShader(lampShaderProgram, lampFragmentShader); //Attach Fragment shader to the Shader program
glLinkProgram(lampShaderProgram); //Link Vertex and Fragment shaders to the Shader program
//Delete the lamp shaders once linked
glDeleteShader(lampVertexShader);
glDeleteShader(lampFragmentShader);
}
/*Creates the Buffer and Array Objects*/
void UCreateBuffers()
{
//Position and Texture coordinate data for 18 triangles
GLfloat vertices[] = {
//Positions //Normals //Texture Coordinates
//Back Face //Negative Z Normals
0.0f, 0.5f, 0.0f, 0.0f, 0.0f, -1.0f, 0.5f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f,
//Front Face //Positive Z Normals
0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.5f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f,
//Left Face //Negative X Normals
0.0f, 0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 0.5f, 1.0f,
-0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 0.0f,
-0.5f, -0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
//Right Face //Positive X Normals
0.0f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.5f, 1.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f,
0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
//Bottom Face //Negative Y Normals
-0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 0.0f,
0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f,
};
//Generate buffer ids
glGenVertexArrays(1, &PyramidVAO);
glGenBuffers(1, &VBO);
//Activate the PyramidVAO before binding and setting VBOs and VAPs
glBindVertexArray(PyramidVAO);
//Activate the VBO
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); //Copy vertices to VBO
//Set attribute pointer 0 to hold position data
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(0); //Enables vertex attribute
//Set attribute pointer 1 to hold Normal data
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glEnableVertexAttribArray(1);
//Set attribute pointer 2 to hold Texture coordinate data
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(6 * sizeof(GLfloat)));
glEnableVertexAttribArray(2);
glBindVertexArray(0); //Unbind the pyramid VAO
//Generate buffer ids for lamp (smaller pyramid)
glGenVertexArrays(1, &LightVAO); //Vertex Array for pyramid vertex copies to serve as light source
//Activate the Vertex Array Object before binding and setting any VBOs and Vertex Attribute Pointers
glBindVertexArray(LightVAO);
//Referencing the same VBO for its vertices
glBindBuffer(GL_ARRAY_BUFFER, VBO);
//Set attribute pointer to 0 to hold Position data (used for the lamp)
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(0);
glBindVertexArray(0);
}
/*Generate and load the texture*/
void UGenerateTexture(){
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
int width, height;
unsigned char* image = SOIL_load_image("brick.jpg", &width, &height, 0, SOIL_LOAD_RGB); //Loads texture file
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
glGenerateMipmap(GL_TEXTURE_2D);
SOIL_free_image_data(image);
glBindTexture(GL_TEXTURE_2D, 0); //Unbind the texture
}
/*标题包含*/
#包括
#包括
#包括
//GLM数学标题包含
#包括
#包括
#包括
//土壤图像加载器
#包括“SOIL2/SOIL2.h”
使用名称空间std//标准名称空间
#定义窗口标题“金字塔”//窗口标题宏
/*着色器程序宏*/
#ifndef GLSL
#定义GLSL（版本，源）“#版本”#版本“\n”#源
#恩迪夫
/*着色器、窗口大小初始化、缓冲区和数组对象的变量声明*/
闪烁棱锥体着色器程序，灯着色器程序，窗宽=800，窗高=600；
GLuint VBO、PyramidVAO、LightVAO、纹理；
//学科地位和规模
glm:：vec3金字塔位置（0.0f，0.0f，0.0f）；
glm:：vec3金字塔标度（2.0f）；
//金字塔与浅色
glm:：vec3 objectColor（1.0f、1.0f、1.0f）；
glm:：vec3 lightColor（1.0f、1.0f、1.0f）；
//灯光位置和比例
glm:：vec3光位置（0.5f，0.5f，-3.0f）；
glm:：vec3光标度（0.3f）；
//摄像机位置
glm:：vec3摄像机位置（0.0f，0.0f，-6.0f）；
//摄像机旋转
浮动摄影机旋转=glm:：弧度（-25.0f）；
/*功能原型*/
无效UResizeWindow（int，int）；
无效图形（无效）；
void-UCreateShader（void）；
无效缓冲区（void）；
void-ugenettexture（void）；
/*金字塔顶点着色器源代码*/
常量GLchar*pyramidVertexShaderSource=GLSL（330，
布局（位置=0）在vec3位置；//顶点属性指针0中的顶点数据
vec3法线中的布局（位置=1）//法线的VAP位置1
vec2纹理坐标中的布局（位置=2）；
out vec3 FragmentPos；//用于输出颜色/像素到片段着色器
out vec3 Normal；//用于将传出法线转换为片段着色器
out vec2 MOBILETEXTEROCORCOLDING；
//变换矩阵的全局变量
统一mat4模型；
统一mat4视图；
均匀mat4投影；
void main（）{
gl_Position=projection*view*model*vec4（位置，1.0f）；//将顶点转换为剪辑坐标
FragmentPos=vec3（model*vec4（位置，1.0f））；//仅获取世界空间中的片段/像素位置（排除视图和投影）
Normal=mat3（转置（逆（模型）））*Normal；//仅获取世界空间中的法向量并排除法向转换属性
MobileTextureCoordination=vec2（textureCoordinate.x，1-textureCoordinate.y）；//水平翻转纹理
}
);
/*金字塔碎片着色器源代码*/
常量GLchar*pyramidFragmentShaderSource=GLSL（330，
在vec3 FragmentPos中；//用于传入片段位置
在vec3法线中；//用于传入法线
在vec2 MobileTextureCoordinal中；
out vec4 pyramidColor；//用于将棱锥体颜色输出到GPU
out vec4 gpuTexture；//将颜色数据传递给GPU的变量
//对象颜色、灯光颜色、灯光位置和摄影机/视图位置的统一/全局变量
均匀的vec3颜色；
均匀的vec3浅色；
均匀vec3-lightPos；
统一的vec3视点；
uniform sampler2D uTexture；//在处理多个纹理时非常有用
void main（）{
/*Phong照明模型计算以生成环境光、漫反射和镜面反射组件*/
//计算环境照明
浮动环境强度=0.1f；//设置环境或全局照明强度
vec3 ambient=ambientStrength*lightColor；//生成环境光颜色
//计算漫反射照明
vec3 norm=normalize（Normal）；//将向量规格化为1个单位
vec3 lightDirection=规格化（lightPos-FragmentPos）；//计算光源和屏幕上的碎片/像素之间的距离（灯光方向）
float impact=max（点（norm，lightDirection），0.0）；//通过生成法线和灯光的点积来计算漫反射影响
vec3 diffuse=impact*lightColor；//生成漫反射光颜色
//计算镜面照明
浮动镜面反射强度=0.8f；//设置镜面反射光强度
float highlightSize=128.0f；//设置镜面反射高光大小
vec3 viewDir=规格化（viewPosition-FragmentPos）；//计算视图方向
vec3 reflectDir=反射（-lightDirection，norm）；//计算反射向量
//计算镜面反射分量
float specularComponent=pow（最大值（点（viewDir，反射DIR），0.0），highlightSize）；
vec3镜面反射=镜面反射强度*镜面反射组件*浅色；
//计算phong结果
vec3 phong=（环境光+漫反射光+镜面反射）*对象颜色；
pyramidColor=vec4（phong，1.0f）；//将照明结果发送到GPU
gpuTexture=纹理（uTexture，mobiletexturecoordination）；
}
);
/*灯着色器源代码*/
常量GLchar*lampVertexShaderSource=GLSL（330，
布局（位置=0）在vec3位置；//顶点位置数据的VAP位置0
//变换矩阵的统一/全局变量
统一mat4模型；
统一mat4视图；
均匀mat4投影；
vo
//Calculate phong result
vec3 objectColor = texture(uTexture, mobileTextureCoordinate).xyz;
vec3 phong = (ambient + diffuse) * objectColor + specular;
pyramidColor = vec4(phong, 1.0f); //Send lighting results to GPU
uTextureLoc = glGetUniformLocation(pyramidShaderProgram, "uTexture");
glUniform1i(uTextureLoc, 0); // texture unit 0
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glDrawArrays(GL_TRIANGLES, 0, 18);