下面的代码在执行时会显示一个绿色三角形，会立即闪烁并消失。
我看到这篇帖子：A red rectangle drawn on 2D texture disappears right after being drawn，其中有一个类似的消失三角形的问题，但他的原因是他多次调用Typeface font = Typeface.createFromAsset(getAssets(), "fonts/PrimeRegular.otf");
SpannableString mNewTitle = new SpannableString(menuItem.getTitle());
mNewTitle.setSpan(new CustomMenuItemTypeface("", font), 0, mNewTitle.length(), Spannable.SPAN_INCLUSIVE_INCLUSIVE);
menuItem.setTitle(mNewTitle);
public class CustomMenuItemTypeface extends TypefaceSpan {
private final Typeface newType;
public CustomMenuItemTypeface(String family, Typeface type) {
super(family);
newType = type;
}
private static void applyCustomTypeFace(Paint paint, Typeface tf) {
int oldStyle;
Typeface old = paint.getTypeface();
if (old == null) {
oldStyle = 0;
} else {
oldStyle = old.getStyle();
}
int fake = oldStyle & ~tf.getStyle();
if ((fake & Typeface.BOLD) != 0) {
paint.setFakeBoldText(true);
}
if ((fake & Typeface.ITALIC) != 0) {
paint.setTextSkewX(-0.25f);
}
paint.setTypeface(tf);
}
@Override
public void updateDrawState(TextPaint ds) {
applyCustomTypeFace(ds, newType);
}
@Override
public void updateMeasureState(TextPaint paint) {
applyCustomTypeFace(paint, newType); }}
，但我只有一个实例Swap Buffer中的glutSwapBuffers()。
displayFunc()在代码中，#include <iostream>
#include "OpenGLMatrix.h"
#include "BasicPipelineProgram.h"
using namespace std;
int windowWidth = 1280;
int windowHeight = 720;
char windowTitle[512] = "Simple Green Triangle";
// global variables
OpenGLMatrix *matrix;
GLuint buffer;
BasicPipelineProgram *pipelineProgram;
GLint program;
GLuint vao;
// objects to render
int numVertices = 3;
float positions[9] =
{ -1, -1, -1,
1, -1, -1,
-1, 1, -1 }; // 3 vertices of triangle to render
float colors[12] =
{ 0, 1, 0, 1,
0, 1, 0, 1,
0, 1, 0, 1 }; // all vertices green with alpha = 1
void bindProgram() {
// upload model view matrix to shader
float m[16];
matrix->SetMatrixMode(OpenGLMatrix::ModelView);
matrix->GetMatrix(m);
pipelineProgram->SetModelViewMatrix(m);
// upload projection matrix to shader
float p[16];
matrix->SetMatrixMode(OpenGLMatrix::Projection);
matrix->GetMatrix(p);
pipelineProgram->SetProjectionMatrix(p);
}
void displayFunc() {
// computing modelview matrix
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
matrix->LoadIdentity();
// camera at (0,0,1), looking in -z direction, up vector y
matrix->LookAt(0, 0, 1, 0, 0, -1, 0, 1, 0);
bindProgram();
// use the VAO
pipelineProgram->Bind();
glBindVertexArray(vao);
GLint first = 0;
GLsizei count = numVertices;
glDrawArrays(GL_TRIANGLES, first, count);
glBindVertexArray(0);
glutSwapBuffers();
}
void idleFunc() {
// make the screen update
glutPostRedisplay();
}
void reshapeFunc(int w, int h) {
GLfloat aspect = (GLfloat) w / (GLfloat) h;
glViewport(0, 0, w, h);
// setup perspective matrix
matrix->SetMatrixMode(OpenGLMatrix::Projection);
matrix->LoadIdentity();
matrix->Perspective(60.0, aspect, 0.01, 1000.0);
matrix->SetMatrixMode(OpenGLMatrix::ModelView);
}
void initPipelineProgram() {
// initialize shader pipeline program
pipelineProgram = new BasicPipelineProgram();
pipelineProgram->Init();
pipelineProgram->Bind();
program = pipelineProgram->GetProgramHandle();
// VAO (vertex array objects) to contain the VBOs
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
// get location index of the "position" shader variable
GLuint loc = glGetAttribLocation(program, "position");
glEnableVertexAttribArray(loc);
const void *offset = (const void*) 0;
GLsizei stride = 0;
GLboolean normalized = GL_FALSE;
glVertexAttribPointer(loc, 3, GL_FLOAT, normalized, stride, offset);
// get location index of the "color" shader variable
loc = glGetAttribLocation(program, "color");
glEnableVertexAttribArray(loc);
offset = (const void*) sizeOfPositions;
stride = 0;
normalized = GL_FALSE;
glVertexAttribPointer(loc, 4, GL_FLOAT, normalized, stride, offset);
glBindVertexArray(0);
}
void initVBO() {
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, sizeOfPositions + sizeOfColors, NULL, GL_STATIC_DRAW);
// upload position data
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeOfPositions, positions);
// upload color data
glBufferSubData(GL_ARRAY_BUFFER, sizeOfPositions, sizeOfColors, colors);
}
void initScene(int argc, char *argv[])
{
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glEnable(GL_DEPTH_TEST);
matrix = new OpenGLMatrix();
initVBO();
initPipelineProgram();
}
int main(int argc, char *argv[])
{
cout << "Initializing GLUT..." << endl;
glutInit(&argc,argv);
cout << "Initializing OpenGL..." << endl;
#ifdef __APPLE__
glutInitDisplayMode(GLUT_3_2_CORE_PROFILE | GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL);
#else
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL);
#endif
glutInitWindowSize(windowWidth, windowHeight);
glutInitWindowPosition(0, 0);
glutCreateWindow(windowTitle);
// glut callback functions
glutDisplayFunc(displayFunc);
glutIdleFunc(idleFunc);
glutReshapeFunc(reshapeFunc);
initScene(argc, argv);
glutMainLoop();
}
和OpenGLMatrix *matrix是在别处定义的类，除非有要求，否则我们的代码我认为不需要担心。 BasicPipelineProgram *pipelineProgram中的"position"和"color"引用 GLSL着色器规范中的变量：
initPipelineProgram()我是OpenGL的初学者，非常感谢任何帮助。谢谢！