我在使用OpenGL 3实现渲染到纹理时遇到了麻烦。
我的问题是渲染到帧缓冲区后，渲染对象变得变形，这可能意味着在某处发生了错误的转换。当不使用我的帧缓冲区时，对象呈现正常时没有意义（见帖子底部）。
目前的结果如下：
Current result http://k.minus.com/jZVgUuLYRtapv.jpg
预期的结果就是这个（或类似的东西，这只是GIMP）： Expected http://k.minus.com/jA5rLM8lmXQYL.jpg
因此，这意味着我在帧缓冲区设置代码或其他地方做错了。但我看不清楚。通过以下功能设置FBO：
unsigned int fbo_id;
unsigned int depth_buffer;
int m_FBOWidth, m_FBOHeight;
unsigned int m_TextureID;
void initFBO() {
m_FBOWidth = screen_width;
m_FBOHeight = screen_height;
glGenRenderbuffers(1, &depth_buffer);
glBindRenderbuffer(GL_RENDERBUFFER, depth_buffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, m_FBOWidth, m_FBOHeight);
glGenTextures(1, &m_TextureID);
glBindTexture(GL_TEXTURE_2D, m_TextureID);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, m_FBOWidth, m_FBOHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glGenFramebuffers(1, &fbo_id);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo_id);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_buffer);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_TextureID, 0);
assert(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
这是我的绘图框代码，它只需要一个转换矩阵并调用相应的函数。 P的当前值是投影矩阵，以及视图矩阵（V）的单位矩阵。
void drawBox(const Matrix4& M) {
const Matrix4 MVP = M * V * P;
if (boundshader) {
glUniformMatrix4fv((*boundshader)("MVP"), 1, GL_FALSE, &MVP[0]);
}
glBindVertexArray(vaoID);
glDrawElements(GL_TRIANGLES, sizeof(cube.polygon)/sizeof(cube.polygon[0]), GL_UNSIGNED_INT, 0);
}
void drawStaticBox() {
Matrix4 M(1);
translate(M, Vector3(0,0,-50));
drawBox(M);
}
void drawRotatingBox() {
Matrix4 M(1);
rotate(M, rotation(Vector3(1, 0, 0), rotation_x));
rotate(M, rotation(Vector3(0, 1, 0), rotation_y));
rotate(M, rotation(Vector3(0, 0, 1), rotation_z));
translate(M, Vector3(0,0,-50));
drawBox(M);
}
GLUT调用显示功能。
void OnRender() {
/////////////////////////////////////////
// Render to FBO
glClearColor(0, 0, 0.2f,0);
glBindFramebuffer(GL_FRAMEBUFFER, fbo_id);
glViewport(0, 0, m_FBOWidth, m_FBOHeight);
glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT);
GL_CHECK_ERRORS
colorshader.Use();
boundshader = &colorshader;
drawRotatingBox();
colorshader.UnUse();
/////////////////////////////////////////
// Render to Window
glClearColor(0, 0, 0, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glViewport(0, 0, screen_width, screen_height);
glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT);
GL_CHECK_ERRORS
texshader.Use();
boundshader = &texshader;
glBindTexture(GL_TEXTURE_2D, m_TextureID);
drawStaticBox();
texshader.UnUse();
// Swap le buffers
glutSwapBuffers();
}
并且......强制纹理着色器代码
顶点
#version 330
in vec2 vUV;
in vec3 vVertex;
smooth out vec2 vTexCoord;
uniform mat4 MVP;
void main()
{
vTexCoord = vUV;
gl_Position = MVP*vec4(vVertex,1);
}
片段
#version 330
smooth in vec2 vTexCoord;
out vec4 vFragColor;
uniform sampler2D textureMap;
void main(void)
{
vFragColor = texture(textureMap, vTexCoord);
}
以下是不使用FBO逻辑时的渲染内容： What is rendered to the FBO http://k.minus.com/jiP7kTOSLLvHk.jpg
...帮助？
关于我可能做错的任何想法？ 可根据要求提供更多来源。
答案 0 :(得分：2)
不仔细查看您的代码，这是一些可行的FBO代码示例（将茶壶动画为纹理，将纹理绘制到旋转立方体的两侧）。
#include <GL/glew.h>
#include <GL/glut.h>
#include <cmath>
#include <iostream>
using namespace std;
namespace render
{
int width, height;
float aspect;
void init();
void reshape(int width, int height);
void display();
int const fbo_width = 512;
int const fbo_height = 512;
GLuint fb, color, depth;
};
void idle();
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH );
glutCreateWindow("FBO test");
glutDisplayFunc(render::display);
glutReshapeFunc(render::reshape);
glutIdleFunc(idle);
glewInit();
render::init();
glutMainLoop();
return 0;
}
void idle()
{
glutPostRedisplay();
}
void CHECK_FRAMEBUFFER_STATUS()
{
GLenum status;
status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
switch(status) {
case GL_FRAMEBUFFER_COMPLETE:
break;
case GL_FRAMEBUFFER_UNSUPPORTED:
/* choose different formats */
break;
default:
/* programming error; will fail on all hardware */
throw "Framebuffer Error";
}
}
namespace render
{
float const light_dir[]={1,1,1,0};
float const light_color[]={1,0.95,0.9,1};
void init()
{
glGenFramebuffers(1, &fb);
glGenTextures(1, &color);
glGenRenderbuffers(1, &depth);
glBindFramebuffer(GL_FRAMEBUFFER, fb);
glBindTexture(GL_TEXTURE_2D, color);
glTexImage2D( GL_TEXTURE_2D,
0,
GL_RGBA,
fbo_width, fbo_height,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);
glBindRenderbuffer(GL_RENDERBUFFER, depth);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, fbo_width, fbo_height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth);
CHECK_FRAMEBUFFER_STATUS();
}
void reshape(int width, int height)
{
render::width=width;
render::height=height;
aspect=float(width)/float(height);
glutPostRedisplay();
}
void prepare()
{
static float a=0, b=0, c=0;
glBindTexture(GL_TEXTURE_2D, 0);
glEnable(GL_TEXTURE_2D);
glBindFramebuffer(GL_FRAMEBUFFER, fb);
glViewport(0,0,fbo_width, fbo_height);
glClearColor(1,1,1,0);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45, 1, 1, 10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glEnable(GL_LIGHT0);
glEnable(GL_LIGHTING);
glEnable(GL_DEPTH_TEST);
glDisable(GL_CULL_FACE);
glLightfv(GL_LIGHT0, GL_POSITION, light_dir);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_color);
glTranslatef(0,0,-5);
glRotatef(a, 1, 0, 0);
glRotatef(b, 0, 1, 0);
glRotatef(c, 0, 0, 1);
glutSolidTeapot(0.75);
a=fmod(a+0.1, 360.);
b=fmod(b+0.5, 360.);
c=fmod(c+0.25, 360.);
}
void final()
{
static float a=0, b=0, c=0;
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glViewport(0,0, width, height);
glClearColor(1.,1.,1.,0.);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45, aspect, 1, 10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0,0,-5);
glRotatef(b, 0, 1, 0);
b=fmod(b+0.5, 360.);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, color);
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDisable(GL_LIGHTING);
float cube[][5]=
{
{-1, -1, -1, 0, 0},
{ 1, -1, -1, 1, 0},
{ 1, 1, -1, 1, 1},
{-1, 1, -1, 0, 1},
{-1, -1, 1, -1, 0},
{ 1, -1, 1, 0, 0},
{ 1, 1, 1, 0, 1},
{-1, 1, 1, -1, 1},
};
unsigned int faces[]=
{
0, 1, 2, 3,
1, 5, 6, 2,
5, 4, 7, 6,
4, 0, 3, 7,
3, 2, 6, 7,
4, 5, 1, 0
};
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(3, GL_FLOAT, 5*sizeof(float), &cube[0][0]);
glTexCoordPointer(2, GL_FLOAT, 5*sizeof(float), &cube[0][3]);
glCullFace(GL_BACK);
glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, faces);
glCullFace(GL_FRONT);
glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, faces);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}
void display()
{
prepare();
final();
glutSwapBuffers();
}
}
仅供参考，以便有一些有用的东西。
答案 1 :(得分：0)
不确定为什么要在着色器中乘以矩阵。假设您想要在屏幕上拉伸渲染到纹理纹理，您只需要定义4个顶点，在x和y上从-1到1，并将这些顶点传递到着色器（如果您正在绘制，则为4个顶点）当然是一个带有2个三角形的条带。）
在着色器中，只需将顶点乘以0.5并添加0.5即可获得纹理坐标。因此，您不需要传递纹理坐标，因为您可以直接在顶点着色器中生成这些坐标。如果将顶点定义为-1到1，则顶点已经在屏幕空间中，因此除了从顶点着色器中发射它们之外，您不需要对它们执行任何操作。
答案 2 :(得分：0)
正如Jari Komppa on GameDev.stackexchange所指出的那样，neodelphi是对我主要帖子的评论。
纹理坐标错误（或者在我的情况下，未通过）。