我已经成功创建了一个VAO，它可以生成一个三角形，然后可以用鼠标旋转（在着色器的帮助下）。
当我尝试使用标准的'glBegin（）'和'glEnd（）'函数绘制其他东西时，我的问题出现了。它成功绘制，但现在，当我尝试旋转三角形时，新绘图也会旋转。
我知道问题以某种方式使用glUseProgram（）函数修复，但我不完全确定应该添加的原因或位置。
这是我的代码（我已经添加了所有内容，但焦点的主要区域应该是display（）和init（）函数：
#include <GL/glew/glew.h>
#include <GL/freeglut.h>
#include <CoreStructures\CoreStructures.h>
#include <iostream>
#include "texture_loader.h"
#include "shader_setup.h"
using namespace std;
using namespace CoreStructures;
float theta = 0.0f;
bool mDown = false;
int mouse_x, mouse_y;
GLuint myShaderProgram;
GLuint locT; // location of "T" uniform variable in myShaderProgram
GLuint locR; // location of "R" uniform variable in myShaderProgram
GLuint sunPosVBO, sunColourVBO, sunIndicesVBO, sunVAO;
// Packed vertex arrays for the star object
// 1) Position Array - Store vertices as (x,y) pairs
static GLfloat sunVertices [] = {
-0.1f, 0.7f,
0.1f, 0.7f,
0.0f, 0.55f
};
// 2) Colour Array - Store RGB values as unsigned bytes
static GLubyte sunColors [] = {
255, 0, 0, 255,
255, 255, 0, 255,
0, 255, 0, 255
};
// 4) Index Array - Store indices to star vertices - this determines the order the vertices are to be processed
static GLubyte sunVertexIndices [] = {0, 1, 2};
void setupSunVAO(void) {
glGenVertexArrays(1, &sunVAO);
glBindVertexArray(sunVAO);
// copy star vertex position data to VBO
glGenBuffers(1, &sunPosVBO);
glBindBuffer(GL_ARRAY_BUFFER, sunPosVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(sunVertices), sunVertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid*)0);
// copy star vertex colour data to VBO
glGenBuffers(1, &sunColourVBO);
glBindBuffer(GL_ARRAY_BUFFER, sunColourVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(sunColors), sunColors, GL_STATIC_DRAW);
glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 0, (const GLvoid*)0);
// enable position, colour buffer inputs
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
// setup star vertex index array
glGenBuffers(1, &sunIndicesVBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, sunIndicesVBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(sunVertexIndices), sunVertexIndices, GL_STATIC_DRAW);
glBindVertexArray(0);
}
void report_version(void) {
int majorVersion, minorVersion;
glGetIntegerv(GL_MAJOR_VERSION, &majorVersion);
glGetIntegerv(GL_MINOR_VERSION, &minorVersion);
cout << "OpenGL version " << majorVersion << "." << minorVersion << "\n\n";
}
void init(void) {
// initialise glew library
GLenum err = glewInit();
// ensure glew was initialised successfully before proceeding
if (err==GLEW_OK)
cout << "GLEW initialised okay\n";
else
cout << "GLEW could not be initialised\n";
report_version();
glClearColor(0.0, 0.0, 0.0, 0.0);
//
// setup "sun" VBO and VAO object
//
setupSunVAO();
//
// load shader program
//
myShaderProgram = setupShaders(string("Resources\\Shaders\\basic_vertex_shader.txt"), string("Resources\\Shaders\\basic_fragment_shader.txt"));
// get the index / location of the uniform variables "T" and "R" in shader program "myShaderProgram"
locT = glGetUniformLocation(myShaderProgram, "T");
locR = glGetUniformLocation(myShaderProgram, "R");
// "plug-in" shader into GPU pipeline
glUseProgram(myShaderProgram); // we're in the driving seat!!!!! Our shaders now intercept and process our vertices as part of the GPU rendering pipeline (as shown in the lecture notes)
}
// Example rendering functions - draw objects in local, or modelling coordinates
void drawSun(void) {
glBindVertexArray(sunVAO);
glDrawElements(GL_TRIANGLE_STRIP, 3, GL_UNSIGNED_BYTE, (GLvoid*)0);
}
void drawShape()
{
glColor3f(0.0f, 0.6f, 0.2f);
glBegin(GL_POLYGON);
glVertex2f(-1.0f, -1.0f); // Left
glVertex2f(-1.0f, -0.1f);
glVertex2f(-0.9f, -0.05f);
glVertex2f(-0.55f, -0.045f);
glVertex2f(-0.49f, -0.06f);
glVertex2f(-0.4f, -0.055f);
glVertex2f(-0.2f, -0.052f);
glVertex2f(0.0f, -0.02f); // Middle
glVertex2f(0.3f, -0.085f);
glVertex2f(0.5f, -0.08f);
glVertex2f(0.8f, -0.088f);
glVertex2f(1.0f, -0.1f);
glVertex2f(1.0f, -1.0f); // Right
glEnd();
}
//
//
void drawScene()
{
drawSun();
drawShape();
}
void display(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Setup translation matrix and store in T. Pass this over the the shader with the function glUniformMatrix4fv
GUMatrix4 T = GUMatrix4::translationMatrix(0.01f, 0.01f, 0.0f);
glUniformMatrix4fv(locT, 1, GL_FALSE, (GLfloat*)&T);
// Setup rotation matrix and store in R. Pass this over the the shader with the function glUniformMatrix4fv
GUMatrix4 R = GUMatrix4::rotationMatrix(0.0f, 0.0f, theta);
glUniformMatrix4fv(locR, 1, GL_FALSE, (GLfloat*)&R);
// Draw the scene (the above transformations will be applied to each vertex in the vertex shader)
drawScene();
glutSwapBuffers();
}
void mouseButtonDown(int button_id, int state, int x, int y) {
if (button_id==GLUT_LEFT_BUTTON) {
if (state==GLUT_DOWN) {
mouse_x = x;
mouse_y = y;
mDown = true;
} else if (state == GLUT_UP) {
mDown = false;
}
}
}
void mouseMove(int x, int y) {
if (mDown) {
int dx = x - mouse_x;
int dy = y - mouse_y;
float delta_theta = (float)dy * (3.142f * 0.01f);
theta += delta_theta;
mouse_x = x;
mouse_y = y;
glutPostRedisplay();
}
}
void keyDown(unsigned char key, int x, int y) {
if (key=='r') {
theta = 0.0f;
glutPostRedisplay();
}
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
initCOM();
glutInitContextVersion(3, 3);
glutInitContextProfile (GLUT_COMPATIBILITY_PROFILE);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(800, 800);
glutInitWindowPosition(0, 0);
glutCreateWindow("Combining Transforms");
glutDisplayFunc(display);
glutKeyboardFunc(keyDown);
glutMouseFunc(mouseButtonDown);
glutMotionFunc(mouseMove);
init();
glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE, GLUT_ACTION_GLUTMAINLOOP_RETURNS);
glutMainLoop();
shutdownCOM();
return 0;
}
修改 的 我有一个x，y顶点数组，我试图将它们与上面的代码一起绘制。出于某种原因，这似乎从sunVAO获取顶点数据。
是否需要清除某种缓存？我搜索过谷歌，但我似乎无法找到其他有VAO和顶点阵列冲突的人。
（另外，我检查了我的代码，并且顶点数组中提供的顶点数据是正确的，它们只是没有正确显示。）
代码：
static GLfloat bottomMarkerVertices[] = {
-0.045f, -0.75f,
0.045f, -0.75f,
-0.07f, -1.0f,
0.07f, -1.0f
};
glVertexPointer(2, GL_FLOAT, 0, bottomMarkerVertices);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
注意：已启用顶点数组。
答案 0 :(得分：0)
场景的两个元素一起移动，因为它们都使用相同的转换矩阵，具体如下：
// Setup translation matrix and store in T. Pass this over the the shader with the function glUniformMatrix4fv
GUMatrix4 T = GUMatrix4::translationMatrix(0.01f, 0.01f, 0.0f);
glUniformMatrix4fv(locT, 1, GL_FALSE, (GLfloat*)&T);
// Setup rotation matrix and store in R. Pass this over the the shader with the function glUniformMatrix4fv
GUMatrix4 R = GUMatrix4::rotationMatrix(0.0f, 0.0f, theta);
glUniformMatrix4fv(locR, 1, GL_FALSE, (GLfloat*)&R);
如果您希望drawShape()不能随鼠标移动，则需要在调用之前重置locR theta值。
drawSun();
GUMatrix4 R = GUMatrix4::rotationMatrix(0.0f, 0.0f, 0.0f);
glUniformMatrix4fv(locR, 1, GL_FALSE, (GLfloat*)&R);
drawShape();
答案 1 :(得分：0)
假设您在标准化设备空间中定义坐标（由明显缺少投影矩阵表示），渲染循环需要看起来像这样：
void drawScene()
{
//update shader parameters for the sun shader if necessary
drawSun();
glUseProgram(0);
// at this point, the PROJECTION and MODELVIEW matrices are both the identity
// so the shape is expected to be in NDCs and is not to be transformed
// at all
drawShape();
glUseProgram(progForSun);
}
请注意，我不建议将旧版和现代版OpenGL混合使用。 drawShape()触发的顶点处理结果仅定义，因为您使用的是兼容性配置文件上下文。