我正在使用com.jogamp.opengl.GL2
在屏幕外渲染3d纹理,然后通过glReadPixels
解析结果。当我的3d纹理值都是正值时,结果就是我所期望的。但是当我有负值时,我无法弄清楚如何配置opengl来给出正确的结果。我试过glPixelStorei(GL2.GL_PACK_SWAP_BYTES, 1);
和glPixelStorei(GL2.GL_UNPACK_SWAP_BYTES, 1);
。我已经尝试了GL_PACK / UNPACK_SWAP_BYTES的所有4种组合,并且所有结果都不正确。
数据范围从-1024到+1024(或在该范围附近),因此作为替代方案,我在(+ 4096然后-4096为良好测量)之后进行标准化和非规范化。这给了我正确的结果,但感觉非常hacky。有没有正确的方法来呈现和解析签名的16位通过Java?
这是基本代码:
private int upload3DTexture(GL2 gl2, ShortBuffer data)
{
int texName[] = new int[1];
gl2.glPixelStorei(GL2.GL_PACK_ALIGNMENT, 2);
gl2.glPixelStorei(GL2.GL_UNPACK_ALIGNMENT, 2);
gl2.glPixelStorei(GL2.GL_PACK_SWAP_BYTES, 1);
gl2.glPixelStorei(GL2.GL_UNPACK_SWAP_BYTES, 1);
gl2.glGenTextures(1, texName, 0);
gl2.glEnable(GL2.GL_TEXTURE_3D);
gl2.glBindTexture(GL2.GL_TEXTURE_3D, texName[0]);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_WRAP_S, GL2.GL_CLAMP_TO_BORDER);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_WRAP_T, GL2.GL_CLAMP_TO_BORDER);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_WRAP_R, GL2.GL_CLAMP_TO_BORDER);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_MAG_FILTER, GL.GL_LINEAR);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_MIN_FILTER, GL.GL_LINEAR);
gl2.glTexEnvi(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_ENV_MODE, GL2.GL_MODULATE);
((java.nio.Buffer)data).rewind();
gl2.glTexImage3D(GL2.GL_TEXTURE_3D, 0, GL2.GL_R16, nCols, nRows, nSlices, 0, GL2.GL_RED, GL.GL_SHORT, data);
return texName[0];
}
private int upload3DTexture(GL2 gl2, ShortBuffer data)
{
int texName[] = new int[1];
gl2.glPixelStorei(GL2.GL_PACK_ALIGNMENT, 2);
gl2.glPixelStorei(GL2.GL_UNPACK_ALIGNMENT, 2);
gl2.glPixelStorei(GL2.GL_PACK_SWAP_BYTES, 1);
gl2.glPixelStorei(GL2.GL_UNPACK_SWAP_BYTES, 1);
gl2.glGenTextures(1, texName, 0);
gl2.glEnable(GL2.GL_TEXTURE_3D);
gl2.glBindTexture(GL2.GL_TEXTURE_3D, texName[0]);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_WRAP_S, GL2.GL_CLAMP_TO_BORDER);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_WRAP_T, GL2.GL_CLAMP_TO_BORDER);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_WRAP_R, GL2.GL_CLAMP_TO_BORDER);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_MAG_FILTER, GL.GL_LINEAR);
gl2.glTexParameteri(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_MIN_FILTER, GL.GL_LINEAR);
gl2.glTexEnvi(GL2.GL_TEXTURE_3D, GL2.GL_TEXTURE_ENV_MODE, GL2.GL_MODULATE);
((java.nio.Buffer)data).rewind();
gl2.glTexImage3D(GL2.GL_TEXTURE_3D, 0, GL2.GL_R16, nCols, nRows, nSlices, 0, GL2.GL_RED, GL.GL_SHORT, data);
return texName[0];
}
private short[] renderAndResolve() {
short[] volume= new short[64];
short index = 0;
for (int z = 0; z < 4; z++) {
for (int y = 0; y < 4; y++) {
for (int x = 0; x < 4; x++) {
volume[index] = (short)(-100*z + y);
index++;
}
}
}
ShortBuffer shortBuffer = ShortBuffer.wrap(volume);
texID = upload3DTexture(gl2, shortBuffer);
display();
ShortBuffer resultBuffer = ShortBuffer.allocate(nSlices * nRows);
resolve(resultBuffer, 4, 4);
return resolve.array();
}
private void resolveDisplay(ShortBuffer slice, int w, int h)
{
GL2 gl2 = drawable.getGL().getGL2(); // The object that contains all the OpenGL methods.
fbo.bind(gl2);
gl2.glReadBuffer(GL2.GL_COLOR_ATTACHMENT0);
((java.nio.Buffer)slice).rewind();
int xd = (frameWidth - w)/2;
int yd = (frameHeight - h)/2;
gl2.glReadPixels(xd, yd, w, h, GL2.GL_RED, GL2.GL_SHORT, slice);
fbo.unbind(gl2);
((java.nio.Buffer)slice).rewind();
}
问题是由纹理的内部格式引起的。
gl2.glTexImage3D(GL2.GL_TEXTURE_3D, 0, GL2.GL_R16, nCols, nRows, nSlices, 0, GL2.GL_RED, GL.GL_SHORT, data);
纹理图像的数据存储的内部格式GL_R16
不是烧结格式,而是无符号整数16位格式。
我不知道你使用的是哪个OpenGL版本。
Desktop OpenGL提供内部数据格式GL_R16_SNORM
,这是一种16位有符号整数数据格式 - 请参阅glTexImage3D
。
GL_R16_SNORM
在接口GL2GL3
中实现:
gl2.glTexImage3D(GL2.GL_TEXTURE_3D, 0, GL2GL3.GL_R16_SNORM,
nCols, nRows, nSlices, 0, GL2.GL_RED, GL.GL_SHORT, data);
OpenGL ES(3.0)提供了一个烧结的整数8位格式GL_R8_SNORM
。
GL_R8_SNORM
实现了接口GL2ES3
:
gl2.glTexImage3D(GL2.GL_TEXTURE_3D, 0, GL2ES3.GL_R8_SNORM,
nCols, nRows, nSlices, 0, GL2.GL_RED, GL.GL_SHORT, data);
作为桌面OpenGL和OpenGL ES的替代方案,提供16浮点格式:
EG
gl2.glTexImage3D(GL2.GL_TEXTURE_3D, 0, GL2.GL_R16F,
nCols, nRows, nSlices, 0, GL2.GL_RED, GL.GL_SHORT, data);