我见过的所有教程都使用单个对象,例如三角形或立方体。但我不清楚如何独立操作单独的对象。我看过一些参考固定函数管道并使用 pushmatrix 和 popmatrix 的教程,但是使用可编程管道,这些函数就消失了。下面是一个 init 函数和一个 draw 函数,它们在屏幕上绘制一个三角形并围绕 Z 轴旋转它。有人可以给我看代码,甚至是伪代码来添加第二个三角形并独立于另一个三角形旋转它吗?说围绕不同的轴或相反的方向?
他们来了:
int Init(ESContext* esContext)
{
UserData* userData = (UserData *)esContext->userData;
const char *vShaderStr =
"attribute vec4 vPosition; \n"
"uniform mat4 MVPMatrix;"
"void main() \n"
"{ \n"
" gl_Position = MVPMatrix * vPosition;\n"
"} \n";
const char *fShaderStr =
"precision mediump float; \n"
"void main() \n"
"{ \n"
" gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); \n"
"} \n";
GLuint vertexShader;
GLuint fragmentShader;
GLuint programObject;
GLint linked;
GLfloat ratio = 320.0f/240.0f;
vertexShader = LoadShader(GL_VERTEX_SHADER, vShaderStr);
fragmentShader = LoadShader(GL_FRAGMENT_SHADER, fShaderStr);
programObject = glCreateProgram();
if (programObject == 0)
return 0;
glAttachShader(programObject, vertexShader);
glAttachShader(programObject, fragmentShader);
glBindAttribLocation(programObject, 0, "vPosition");
glLinkProgram(programObject);
glGetProgramiv(programObject, GL_INFO_LOG_LENGTH, &linked);
if (!linked)
{
GLint infoLen = 0;
glGetProgramiv(programObject, GL_INFO_LOG_LENGTH, &infoLen);
if (infoLen > 1)
{
char* infoLog = (char *)malloc(sizeof(char) * infoLen);
glGetProgramInfoLog(programObject, infoLen, NULL, infoLog);
free(infoLog);
}
glDeleteProgram(programObject);
return FALSE;
}
userData->programObject = programObject;
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glViewport(0, 0, esContext->width, esContext->height);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(userData->programObject);
userData->angle = 0.0f;
userData->start = time(NULL);
userData->ProjMatrix = PVRTMat4::Perspective(ratio*2.0f, 2.0f, 3.0f, 7.0f, PVRTMat4::eClipspace::OGL, false, false);
userData->ViewMatrix = PVRTMat4::LookAtLH(PVRTVec3(0.0f, 0.0f, -3.0f), PVRTVec3(0.0f, 0.0f, 0.0f), PVRTVec3(0.0f, 1.0f, 0.0f));
return TRUE;
}
void Draw(ESContext *esContext)
{
GLfloat vVertices[] = {0.0f, 0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f};
GLint MVPHandle;
double timelapse;
PVRTMat4 MVPMatrix = PVRTMat4::Identity();
UserData* userData = (UserData *)esContext->userData;
timelapse = difftime(time(NULL), userData->start) * 1000;
if(timelapse > 16.0f) //Maintain approx 60FPS
{
if (userData->angle > 360.0f)
{
userData->angle = 0.0f;
}
else
{
userData->angle += 0.1f;
}
}
userData->ModelMatrix = PVRTMat4::RotationZ(userData->angle);
MVPMatrix = userData->ViewMatrix * userData->ModelMatrix;
MVPMatrix = userData->ProjMatrix * MVPMatrix;
MVPHandle = glGetUniformLocation(userData->programObject, "MVPMatrix");
glUniformMatrix4fv(MVPHandle, 1, FALSE, MVPMatrix.ptr());
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, vVertices);
glEnableVertexAttribArray(0);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface);
}