从单个 OpenGL ES 纹理渲染多个精灵

Question

我是 OpenGL ES 1.1 的新手，我正在尝试通过创建一组函数来慢慢开始，这些函数将在我的 iPhone 上从单个纹理渲染多个精灵。我的工作正如我所期望的那样（但如果我犯了任何明显的错误，请告诉我），但现在我正在寻找优化我的代码。因此，我有两个问题：

1) 我怎样才能加快下面的代码？据我了解，我应该能够从同一个 OpenGL 纹理批量调用多个绘制调用以加快渲染速度。我该怎么做，有什么好的代码示例我应该注意吗？

2) 使用 glOrthof 我将坐标系更改为从 0、0 到我的设备宽度和高度。在传递 glTexCoordPointer 纹理坐标时，是否有类似的处理方式可以让我传递像素值？

供参考，这是我的代码：

- (void)drawGLView
{
    [EAGLContext setCurrentContext:context];

    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);

    glClearColor( 0, 0, 0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glBindTexture(GL_TEXTURE_2D, spriteTexture);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    for(Sprite *sprite in self.sprites)
    {
        [self drawAtPoint:sprite.location];
    }
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);

    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
    [context presentRenderbuffer:GL_RENDERBUFFER_OES];
}

- (void)drawAtPoint:(CGPoint)point
{
    GLfloat x = point.x, y = point.y;
    GLfloat w = self.spritesheet.size.width;
    GLfloat h = self.spritesheet.size.height;
    GLfloat box[] = {
        x, y + h, 0,
        x, y, 0,
        x + w, y + h, 0,
        x + w, y , 0
    };
    GLfloat tex[] = {
        0, 1,
        0, 0,
        1, 1,
        1, 0
    };

    glVertexPointer(3, GL_FLOAT, 0, box);
    glTexCoordPointer(2, GL_FLOAT, 0, tex);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}

Answer 1

1）这是我用于我的粒子系统的东西（它在 c++ 中，但你会明白这一点）。你可以把你的纹理排成一行（水平的，并且都具有相同的大小），然后绘制它使用正确的 id，0-first tex ，1-second 等等；

class gltAtlasRenderer
{
public:
    float* partVdata;
    float* partCdata;
    float* partTdata;

    int counter1,counter2,counter3;
    int count;
    bool isz;
    int tilesize;
    float tilesx;
    gltAtlasRenderer(int maxTextures,bool iszi,int numberoftiles)
    {
        isz=iszi;
        if(isz)partVdata=(float*)malloc(maxTextures*18*4);
        else partVdata=(float*)malloc(maxTextures*12*4);

        partCdata=(float*)malloc(maxTextures*24*4);
        partTdata=(float*)malloc(maxTextures*12*4);
        tilesize=numberoftiles;
        tilesx=(float)(1.0f/numberoftiles);
    }
    void Draw(int id,float x,float y,float z,float scalex,float scaley,float angle,float r,float g,float b,float a)
    {
        angle*=0.017453f;
        for(int c2=0;c2<12;c2+=2)
        {
                float x=squarevData[c2]*scalex;
                float y=squarevData[c2+1]*scaley;
                float cos1=cos(angle);
                float sin1=sin(angle);
                squarevData2[c2] = (cos1*x) - ( sin1*y);
                squarevData2[c2+1] = (sin1*x) + ( cos1*y);
        }


        //up left
        partVdata[counter1++]=x+squarevData2[0];
        partVdata[counter1++]=y+squarevData2[1];
        if(isz)partVdata[counter1++]=z;
        partCdata[counter2++]=r;
        partCdata[counter2++]=g;
        partCdata[counter2++]=b;
        partCdata[counter2++]=a;
        partTdata[counter3++]=tilesx*id;
        partTdata[counter3++]=1;

        //up right
        partVdata[counter1++]=x+squarevData2[2];
        partVdata[counter1++]=y+squarevData2[3];
        if(isz)partVdata[counter1++]=z;
        partCdata[counter2++]=r;
        partCdata[counter2++]=g;
        partCdata[counter2++]=b;
        partCdata[counter2++]=a;
        partTdata[counter3++]=tilesx*id+tilesx;
        partTdata[counter3++]=1;


        //down left
        partVdata[counter1++]=x+squarevData2[4];
        partVdata[counter1++]=y+squarevData2[5];
        if(isz)partVdata[counter1++]=z;
        partCdata[counter2++]=r;
        partCdata[counter2++]=g;
        partCdata[counter2++]=b;
        partCdata[counter2++]=a;
        partTdata[counter3++]=tilesx*id;
        partTdata[counter3++]=0;

        //up right
        partVdata[counter1++]=x+squarevData2[6];
        partVdata[counter1++]=y+squarevData2[7];
        if(isz)partVdata[counter1++]=z;
        partCdata[counter2++]=r;
        partCdata[counter2++]=g;
        partCdata[counter2++]=b;
        partCdata[counter2++]=a;
        partTdata[counter3++]=tilesx*id+tilesx;
        partTdata[counter3++]=1;

        //down right
        partVdata[counter1++]=x+squarevData2[8];
        partVdata[counter1++]=y+squarevData2[9];
        if(isz)partVdata[counter1++]=z;
        partCdata[counter2++]=r;
        partCdata[counter2++]=g;
        partCdata[counter2++]=b;
        partCdata[counter2++]=a;
        partTdata[counter3++]=tilesx*id+tilesx;
        partTdata[counter3++]=0;


        //down left
        partVdata[counter1++]=x+squarevData2[10];
        partVdata[counter1++]=y+squarevData2[11];
        if(isz)partVdata[counter1++]=z;
        partCdata[counter2++]=r;
        partCdata[counter2++]=g;
        partCdata[counter2++]=b;
        partCdata[counter2++]=a;
        partTdata[counter3++]=tilesx*id;
        partTdata[counter3++]=0;

        count++;

    }
    void RenderStart()
    {
        counter1=counter2=count=counter3=0;

    }
    void RenderStop(int textureid)
    {
        glEnable(GL_TEXTURE_2D);
        glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_MODULATE);
        glEnableClientState(GL_COLOR_ARRAY);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);
        glEnableClientState(GL_VERTEX_ARRAY);
        glBindTexture(GL_TEXTURE_2D, textureid);
        glTexCoordPointer(2, GL_FLOAT, 0, partTdata);
        glColorPointer(4, GL_FLOAT, 0,partCdata );
        if(isz)glVertexPointer(3, GL_FLOAT, 0, partVdata);
        else glVertexPointer(2, GL_FLOAT, 0, partVdata);
        glDrawArrays(GL_TRIANGLES, 0, count*6);
        glDisableClientState(GL_COLOR_ARRAY);
        glDisableClientState(GL_TEXTURE_COORD_ARRAY);
        glDisableClientState(GL_VERTEX_ARRAY);

    }
};

gltAtlasRenderer ar=new gltAtlasRenderer(100,false,5);//max textures, is there z,max textures in texture
ar.RenderStart();
void Render()
{
     for(int c=0;c<100;c++)ar.Draw(0,x,y,z,scalex,scaley,rotation,r,g,b,a);
}
ar.RenderStop(textureid);

2）如果我理解正确，您想使用纹理大小的纹理坐标（而不是 0 到 1 的比例）

例如，在 512x512 的纹理中，纹理坐标将为

float cv(float maxsize,float num)
{
     return (num/maxsize);
}

cv(0),cv(0)//bot,left
cv(512),cv(0)//bot,right
cv(512),cv(512)//top,right
cv(0),cv(512)//bot,left