openGL之API学习（二一二）固定管线的纹理

Posted 2022-03-01 hankern

会将固定管线各个纹理单元(openGL之API学习（二零五）GL_MAX_TEXTURE_UNITS GL_MAX_TEXTURE_IMAGE_UNITS_ARB GL_MAX_COMBINED_TEXTURE_IM纹理单元数_hankern的专栏-CSDN博客int _maxFFPTextureUnits;int _maxGPUTextureUnits;glGetIntegerv( GL_MAX_TEXTURE_UNITS, &_maxFFPTextureUnits ); //4glGetIntegerv( GL_MAX_TEXTURE_IMAGE_UNITS_ARB, &_maxGPUTextureUnits ); //32https://blog.csdn.net/hankern/article/details/122911153)的纹理融合显示，融合的规则是各个像素分量取最小值。如果不需要融合，则在每个纹理单元使用完后调用glBindTexture(GL_TEXTURE_2D, 0)。

比如

renderInfor.getState()->setActiveTextureUnit(2);
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);
glDisable(GL_LIGHTING);
glColor4f(1.0,1.0,1.0,1.0);

static GLuint disp_tex_id1=0;
if(disp_tex_id1<=0)
    glGenTextures(1, &disp_tex_id1);



glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, disp_tex_id1);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);


osg::ref_ptr<osg::Image> img1 = new osg::Image;
img1=osgDB::readImageFile("D:\\\\OSG_OAGEARTH_x86\\\\data\\\\school.png");
osg::ref_ptr<osg::Texture2D> tex2 = new osg::Texture2D(img1);
unsigned char* dataPtr1 = (unsigned char*)img1->data();
glTexImage2D( GL_TEXTURE_2D, 0, img1->getInternalTextureFormat(),
              img1->s(), img1->t(), tex2->getBorderWidth(),
              (GLenum)img1->getPixelFormat(),
              (GLenum)img1->getDataType(),
              dataPtr1);



renderInfor.getState()->setActiveTextureUnit(1);
static GLuint disp_tex_id=0;
if(disp_tex_id<=0)
    glGenTextures(1, &disp_tex_id);



glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, disp_tex_id);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);


osg::ref_ptr<osg::Image> img = new osg::Image;
img=osgDB::readImageFile("D:\\\\OSG_OAGEARTH_x86\\\\data\\\\road.png");
osg::ref_ptr<osg::Texture2D> tex1 = new osg::Texture2D(img);
unsigned char* dataPtr = (unsigned char*)img->data();
glTexImage2D( GL_TEXTURE_2D, 0, img->getInternalTextureFormat(),
              img->s(), img->t(), tex1->getBorderWidth(),
              (GLenum)img->getPixelFormat(),
              (GLenum)img->getDataType(),
              dataPtr);


GLfloat vVertices[] =

    -5.0f,0.0f,-5.0f,
    5.0f,0.0f,-5.0f,
    5.0f,0.0f,5.0f,
    -5.0f,0.0f,5.0f
;



GLfloat vTex[] = 
    0.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 1.0f,
    1.0f, 0.0f,
;
GLfloat vColor[] =

    0.8,0.0,0.0,1.0
;

glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 0,vVertices);

state->setClientActiveTextureUnit(1);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 0,vTex);

glDrawArrays(GL_QUADS, 0, 4);

融合后效果

两张纹理图片分别为：