OpenGL绘制（颜色）奇怪的事情，碎片着色器弄乱了什么？
我编写了一个小程序来简单地加载Wavefront OBJ网格文件并使用适当的光照（Phong着色）显示几何体，但渲染似乎有问题，这很奇怪。当我简单地改变我的片段着色器以均匀地着色（没有照明）时，没关系，但每当我将一些规范计算推入我的代码时，问题就会开始出现。
我几乎可以确定问题来自片段着色器和/或法线，因为几何坐标是一致的（转到GL_POINT，点被正确定位），只有着色不能正常工作。
我会把我的代码放在这里;我也会上传渲染的结果。我会感激任何能够找出问题所在的人。
另外这里是天际头盔的OBJ文件！： helmet.obj
注意：我使用math32（包含在GLTools）库中进行透视和其他矩阵计算，可在此处获得： GLTools.zip
渲染功能：
void render(HDC hdc)
{
//Some matrix calculations start
unsigned int tTime=GetTickCount();
float angle=(tLastTime!=0)?(float(GetTickCount()-tLastTime)/(1.0f/speed)):(0);
if(tLastTime==0) tLastTime=GetTickCount();
float projection_matrix[16],rotation_matrix[16],MV_matrix[16],temp_matrix[16];
m3dRotationMatrix44(rotation_matrix,angle,2.0f,4.0f,2.0f);
Rotate(MV_matrix,angle,2.0f,4.0f,2.0f,CenterX,CenterY,CenterZ);
m3dTranslationMatrix44(temp_matrix,-CenterX,-CenterY,(-CenterZ)-40.0f);
Multiply(temp_matrix,MV_matrix);
PerspectiveMatrix(projection_matrix,60.0f,1.0f,0.0001f,1000.0f);
//Some matrix calculations end
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);
glUseProgramObjectARB(pShaderProgram);
glUniformMatrix4fvARB(uniMVMatrix,1,false,MV_matrix);
glUniformMatrix4fvARB(uniProjectionMatrix,1,false,projection_matrix);
glUniformMatrix4fvARB(uniRotationMatrix,1,false,rotation_matrix);
glUniform3fvARB(uniLightPosition,1,light_position);
glBindVertexArray(objVertexArray);
glDrawArrays(GL_TRIANGLES,0,nVertices);
glBindVertexArray(0);
SwapBuffers(hdc);
return;
}
主要功能（上下文创建/初始化）：
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
WNDCLASSEX wndcls;
wndcls.cbSize=sizeof(WNDCLASSEX);
wndcls.cbClsExtra=0;
wndcls.cbWndExtra=0;
wndcls.hbrBackground=(HBRUSH)(COLOR_WINDOW+1);
wndcls.style=CS_HREDRAW|CS_VREDRAW|CS_OWNDC;
wndcls.hCursor=(HCURSOR)LoadCursor(NULL,IDC_ARROW);
wndcls.hIcon=LoadIcon(hInstance,IDI_APPLICATION);
wndcls.hIconSm=NULL;
wndcls.hInstance=hInstance;
wndcls.lpfnWndProc=(WNDPROC)WndProc;
wndcls.lpszClassName="Win32Class";
wndcls.lpszMenuName=NULL;
RegisterClassEx(&wndcls);
HWND hwnd=CreateWindowEx(0,"Win32Class","OpenGL Projekt",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT,1280,720,NULL,NULL,hInstance,NULL);
HDC hdc=GetDC(hwnd);
PIXELFORMATDESCRIPTOR pfd=
{
sizeof(PIXELFORMATDESCRIPTOR),
1,
PFD_DRAW_TO_WINDOW|PFD_SUPPORT_OPENGL|PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA,
32,
0,0,0,0,0,0,
0,
0,
0,
0,0,0,0,
24,
8,
0,
PFD_MAIN_PLANE,
0,
0,0,0
};
int pf=ChoosePixelFormat(hdc,&pfd);
SetPixelFormat(hdc,pf,&pfd);
HGLRC hglrc=wglCreateContext(hdc);
wglMakeCurrent(hdc,hglrc);
setup_extensions(); // using wglGetProcAddress
wglMakeCurrent(hdc,NULL);
DestroyWindow(hwnd); // that was just for getting function pointers!
//Real window/context:
hwnd=CreateWindowEx(0,"Win32Class","OpenGL Projekt",WS_OVERLAPPED|WS_SYSMENU|WS_MINIMIZEBOX|WS_CAPTION,CW_USEDEFAULT,CW_USEDEFAULT,700,722,NULL,NULL,hInstance,NULL);
hdc=GetDC(hwnd);
const int attribs[]={
WGL_DRAW_TO_WINDOW_ARB,1,
WGL_SUPPORT_OPENGL_ARB,1,
WGL_DOUBLE_BUFFER_ARB,1,
WGL_PIXEL_TYPE_ARB,WGL_TYPE_RGBA_ARB,
WGL_COLOR_BITS_ARB,32,
WGL_DEPTH_BITS_ARB,24,
WGL_STENCIL_BITS_ARB,8,
WGL_SAMPLE_BUFFERS_ARB,1, // MSAA enabled
WGL_SAMPLES_ARB,8, // MSAA 8x
0};
int wpf[3];
unsigned int nwpf;
wglChoosePixelFormatARB(hdc,attribs,NULL,3,wpf,&nwpf);
SetPixelFormat(hdc,wpf[0],&pfd);
const int attribs_cc[]={
WGL_CONTEXT_MAJOR_VERSION_ARB,3,
WGL_CONTEXT_MINOR_VERSION_ARB,3,
WGL_CONTEXT_PROFILE_MASK_ARB,WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
0
};
hglrc=wglCreateContextAttribsARB(hdc,NULL,attribs_cc);
wglMakeContextCurrentARB(hdc,hdc,hglrc);
setup();
ShowWindow(hwnd,nShowCmd);
MSG msg;
bool done=false;
while(!done)
{
if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
if(msg.message==WM_QUIT)
done=true;
else
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
else
render(hdc);
}
return (int)msg.wParam;
}
设定：
void setup()
{
glClearColor(0.11,0.11,0.11,1.0);
glEnable(GL_MULTISAMPLE_ARB);
glEnable(GL_DEPTH_TEST);
glDisable(GL_BLEND);
glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
//Shader loading start
FILE *f;
int fsize,status;
char *shadersrc[1];
unsigned int shVertexShader=0,shFragmentShader=0;
shVertexShader=glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
shFragmentShader=glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
f=fopen("VShader","rb");
fseek(f,0,SEEK_END);
fsize=ftell(f);
fseek(f,0,SEEK_SET);
shadersrc[0]=new char[fsize];
fread(shadersrc[0],sizeof(char),fsize,f);
glShaderSourceARB(shVertexShader,1,(const char**)shadersrc,&fsize);
free(shadersrc[0]);
fclose(f);
f=fopen("FShader","rb");
fseek(f,0,SEEK_END);
fsize=ftell(f);
fseek(f,0,SEEK_SET);
shadersrc[0]=new char[fsize];
fread(shadersrc[0],sizeof(char),fsize,f);
glShaderSourceARB(shFragmentShader,1,(const char**)shadersrc,&fsize);
free(shadersrc[0]);
fclose(f);
glCompileShaderARB(shVertexShader);
glGetObjectParameterivARB(shVertexShader,GL_OBJECT_COMPILE_STATUS_ARB,&status);
if(!status)
{
char errinfo[512];
glGetInfoLogARB(shVertexShader,511,NULL,errinfo);
MessageBox(NULL,errinfo,"Error",MB_OK);
exit(EXIT_FAILURE);
}
glCompileShaderARB(shFragmentShader);
glGetObjectParameterivARB(shFragmentShader,GL_OBJECT_COMPILE_STATUS_ARB,&status);
if(!status)
{
char errinfo[512];
glGetInfoLogARB(shFragmentShader,511,NULL,errinfo);
MessageBox(NULL,errinfo,"Error",MB_OK);
exit(EXIT_FAILURE);
}
pShaderProgram=glCreateProgramObjectARB();
glAttachObjectARB(pShaderProgram,shVertexShader);
glAttachObjectARB(pShaderProgram,shFragmentShader);
glBindAttribLocationARB(pShaderProgram,0,"vertices");
glBindAttribLocationARB(pShaderProgram,1,"normals");
glLinkProgramARB(pShaderProgram);
glGetObjectParameterivARB(pShaderProgram,GL_OBJECT_LINK_STATUS_ARB,&status);
if(!status)
{
char errinfo[512];
glGetInfoLogARB(pShaderProgram,511,NULL,errinfo);
MessageBox(NULL,errinfo,"Error",MB_OK);
exit(EXIT_FAILURE);
}
glDeleteObjectARB(shVertexShader);
glDeleteObjectARB(shFragmentShader);
uniMVMatrix=glGetUniformLocationARB(pShaderProgram,"MV_matrix");
uniProjectionMatrix=glGetUniformLocationARB(pShaderProgram,"projection_matrix");
uniRotationMatrix=glGetUniformLocationARB(pShaderProgram,"rotation_matrix");
uniLightPosition=glGetUniformLocationARB(pShaderProgram,"light_position");
//Shader loading end
//Loading from OBJ file start
if(!LoadOBJFile(OBJFile,&vertices,&normals,&nVertices))
{
char msg[700];
sprintf(msg,"Cannot open file \"%s\".",OBJFile);
MessageBox(NULL,msg,"Error",MB_OK);
exit(EXIT_FAILURE);
}
//Loading from OBJ file end
GetCenter(vertices,nVertices,&CenterX,&CenterY,&CenterZ);
light_position[0]=0.0f;
light_position[0]=0.0f;
light_position[0]=4000.0f;
glGenVertexArrays(1,&objVertexArray);
glBindVertexArray(objVertexArray);
glGenBuffers(1,&buffVertexArray);
glBindBuffer(GL_ARRAY_BUFFER,buffVertexArray);
glBufferData(GL_ARRAY_BUFFER,sizeof(float)*3*nVertices,vertices,GL_DYNAMIC_DRAW);
glGenBuffers(1,&buffNormalArray);
glBindBuffer(GL_ARRAY_BUFFER,buffNormalArray);
glBufferData(GL_ARRAY_BUFFER,sizeof(float)*3*nVertices,normals,GL_DYNAMIC_DRAW);
glEnableVertexAttribArrayARB(0);
glEnableVertexAttribArrayARB(1);
glBindBuffer(GL_ARRAY_BUFFER,buffVertexArray);
glVertexAttribPointerARB(0,3,GL_FLOAT,false,0,NULL);
glBindBuffer(GL_ARRAY_BUFFER,buffNormalArray);
glVertexAttribPointerARB(1,3,GL_FLOAT,false,0,NULL);
glBindVertexArray(0);
return;
}
顶点着色器：
#version 330 core
uniform mat4 MV_matrix;
uniform mat4 projection_matrix;
uniform mat4 rotation_matrix;
in vec3 vertices;
in vec3 normals;
smooth out vec3 f_vertices;
smooth out vec3 f_normals;
void main(void)
{
gl_Position=projection_matrix*MV_matrix*vec4(vertices,1.0);
f_vertices=(MV_matrix*vec4(vertices,1.0)).xyz;
f_normals=(rotation_matrix*vec4(normals,1.0)).xyz;
return;
}
片段着色器：
#version 330 core
uniform vec3 light_position;
smooth in vec3 f_vertices;
smooth in vec3 f_normals;
out vec4 fragcolor;
void main(void)
{
vec3 to_light_dir=light_position-f_vertices;
float diff=min(1.0,(dot(normalize(f_normals),normalize(to_light_dir))));
fragcolor=diff*vec4(0.5,0.5,0.5,1.0);
}
OBJ文件加载器：
#include <string>
#include <fstream>
#include <vector>
#include "math3d.h"
struct vertex
{
float x;
float y;
float z;
float w;
};
struct normal
{
float x;
float y;
float z;
};
struct texcoord
{
float u;
float v;
float w;
};
struct face
{
unsigned int vertices[3];
unsigned int normals[3];
unsigned int texcoords[3];
};
using namespace std;
bool LoadOBJFile(const char *path,float **vertices,float **normals,unsigned int *num_vertices)
{
char id[1024];
float fa[9];
int nc;
vertex tvertex;
normal tnormal;
texcoord ttexcoord;
face tface;
bool gotnormal=false;
vector<vertex> _v;
vector<normal> _vn;
vector<texcoord> _vt;
vector<face> _f;
ifstream f(path);
if(!f.is_open()) return false;
for(string line;getline(f,line);)
{
if(line.c_str()[0]=='#' || line.c_str()[0]=='\x0A' || line.c_str()[0]=='\x0D' || line.size()==0) continue;
sscanf(line.c_str(),"%s",id);
if(strcmp(id,"v")==0)
{
if(sscanf(line.c_str(),"%s %f %f %f %f",id,fa,fa+1,fa+2,fa+3)==5)
{
tvertex.x=fa[0];
tvertex.y=fa[1];
tvertex.z=fa[2];
tvertex.w=fa[3];
}else if(sscanf(line.c_str(),"%s %f %f %f",id,fa,fa+1,fa+2)==4)
{
tvertex.x=fa[0];
tvertex.y=fa[1];
tvertex.z=fa[2];
tvertex.w=1.0f;
}else
{
return false;
}
_v.push_back(tvertex);
}else if(strcmp(id,"vn")==0)
{
if(sscanf(line.c_str(),"%s %f %f %f",id,fa,fa+1,fa+2)==4)
{
tnormal.x=fa[0];
tnormal.y=fa[1];
tnormal.z=fa[2];
}else
{
return false;
}
_vn.push_back(tnormal);
}else if(strcmp(id,"vn")==0)
{
if(sscanf(line.c_str(),"%s %f %f %f",id,fa,fa+1,fa+2)==4)
{
ttexcoord.u=fa[0];
ttexcoord.v=fa[1];
ttexcoord.w=fa[2];
}else if(sscanf(line.c_str(),"%s %f %f",id,fa,fa+1)==3)
{
ttexcoord.u=fa[0];
ttexcoord.v=fa[1];
ttexcoord.w=0.0f;
}else if(sscanf(line.c_str(),"%s %f %f %f",id,fa)==2)
{
ttexcoord.u=fa[0];
ttexcoord.v=0.0f;
ttexcoord.w=0.0f;
}else
{
return false;
}
_vt.push_back(ttexcoord);
}else if(strcmp(id,"f")==0)
{
if(sscanf(line.c_str(),"%s %f/%f/%f %f/%f/%f %f/%f/%f",id,fa,fa+1,fa+2,fa+3,fa+4,fa+5,fa+6,fa+7,fa+8)==10)
{
for(int j=0;j<3;j++)
{
tface.vertices[j]=fa[j*3];
tface.normals[j]=fa[j*3+2];
tface.texcoords[j]=fa[j*3+1];
}
}else if(sscanf(line.c_str(),"%s %f//%f %f//%f %f//%f",id,fa,fa+2,fa+3,fa+5,fa+6,fa+8)==7)
{
for(int j=0;j<3;j++)
{
tface.vertices[j]=fa[j*3];
tface.normals[j]=fa[j*3+2];
tface.texcoords[j]=0;
}
}else if(sscanf(line.c_str(),"%s %f/%f %f/%f %f/%f",id,fa,fa+1,fa+3,fa+4,fa+6,fa+7)==7)
{
for(int j=0;j<3;j++)
{
tface.vertices[j]=fa[j*3];
tface.normals[j]=0;
tface.texcoords[j]=fa[j*3+1];
}
}else if(sscanf(line.c_str(),"%s %f %f %f",id,fa,fa+3,fa+6)==4)
{
for(int j=0;j<3;j++)
{
tface.vertices[j]=fa[j*3];
tface.normals[j]=0;
tface.texcoords[j]=0;
}
}else
{
return false;
}
_f.push_back(tface);
}
}
*num_vertices=3*(_f.size());
*vertices=new float[(*num_vertices)*3];
*normals=new float[(*num_vertices)*3];
if(_vn.size() && _f[0].normals[0])
gotnormal=true;
for(unsigned int i=0;i<(*num_vertices)*3;i+=3)
{
int iFc=int(float(i)/9.0f);
int iVr=(i/3)%3;
(*vertices)[i]=_v[_f[iFc].vertices[iVr]-1].x;
(*vertices)[i+1]=_v[_f[iFc].vertices[iVr]-1].y;
(*vertices)[i+2]=_v[_f[iFc].vertices[iVr]-1].z;
if(gotnormal)
{
(*normals)[i]=_vn[_f[iFc].normals[iVr]-1].x;
(*normals)[i+1]=_vn[_f[iFc].normals[iVr]-1].y;
(*normals)[i+2]=_vn[_f[iFc].normals[iVr]-1].z;
}
}
for(unsigned int i=0;i<(*num_vertices)*3 && !gotnormal;i+=9)
{
M3DVector3f norm;
m3dFindNormal(norm,(*vertices)+i,(*vertices)+(i+3),(*vertices)+(i+6));
for(unsigned short j=0;j<9;j+=3)
{
(*normals)[i+j]=norm[0];
(*normals)[i+j+1]=norm[1];
(*normals)[i+j+2]=norm[2];
}
}
_v.~vector();
_f.~vector();
_vt.~vector();
_vn.~vector();
return true;
}
没有照明的结果（diff = 1.0）：
带照明的结果（下面的动画版本）：
动画版 1.avi (5.94MB)
1 个答案:
答案 0 :(得分：2)
在片段着色器中，两个标准化向量的点积不能大于1，因此不必将其钳制为不大于1：
float diff=min(1.0,(dot(normalize(f_normals),normalize(to_light_dir))));
相反，你可以将它钳制到不低于0：
float diff=max(0.0,(dot(normalize(f_normals),normalize(to_light_dir))));
无论如何，我认为还有别的东西会导致问题。它看起来不像错误的法线，它可能相当于一些z战斗。尝试将近距离和远距离平面设置得更近。或者你的几何形状可能很薄？你启用了背面剔除吗？它也可以解决这个问题。您还应该仔细检查您的OBJ加载程序，以确保它是100％正确的，特别是在读取法线时。
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