在片段着色器中访问3D数组 [英] Access to 3D array in fragment shader
问题描述
我正在尝试使用PyOpenGL从Python程序向标量着色器提供对标量数据的3维数组的访问.
I'm trying to provide access to a 3-dimensional array of scalar data to a fragment shader, from a Python program using PyOpenGL.
在片段着色器中，我声明了一个统一的3d采样器
In the fragment shader, I declare the a 3d sampler uniform
uniform sampler3D vol;
在Python程序中，我有以下代码来设置标量3d纹理
and in the Python program I have the following code to set up a scalar 3d texture
vol = numpy.random.rand(3, 3, 3).astype(np.float32)
texture = glGenTextures(1)
glUniform1i(glGetUniformLocation(program, "vol"), 0)
glActiveTexture(GL_TEXTURE0 + 0)
glBindTexture(GL_TEXTURE_3D, texture)
glTexImage3D(GL_TEXTURE_3D, 0, GL_RED, 3, 3, 3, 0, GL_RED, GL_FLOAT, vol)
glEnable(GL_TEXTURE_3D)
但是，无论我从采样器的哪个位置获取值，例如
However, no matter where from the sampler I take values, e.g.
color = texture(vol, vec3(0, 0, 0));
看来我总是得到黑色(0、0、0).
it appears that I always obtain black (0, 0, 0).
我在做什么错了?
我知道片段着色器的基本设置有效，即，如果我写color = vec3(1, 0, 0)，我会得到红色像素.
I know that the basic setup of my fragment shader works, i.e. if I write color = vec3(1, 0, 0) I get red pixels.
我还知道没有OpenGL错误，因为我正在运行由glutInit()处理的选项-glerror的程序，这导致OpenGL错误被转换为Python异常.
I also know that there are no OpenGL errors, because I'm running the program with the option -glerror processed by glutInit(), which leads to OpenGL errors being translated into Python exceptions.
推荐答案
这是因为您的GL_RED纹理格式被固定到了<0,1> !!!
That is because your GL_RED texture format is clamped to range <0,1> !!!
要解决此问题，您需要使用非钳制纹理格式或禁用钳制...以下示例适用于我的GL实现:
To remedy you need to use non clamped texture format or disable clamping ... Here examples that are working on my GL implementations:
- GPU ray casting (single pass) with 3d textures in spherical coordinates
- GLSL back raytrace through 3D volume
此处是从两者中提取的格式:
here formats extracted from both:
glTexImage3D(GL_TEXTURE_3D, 0, GL_R16F, xs,ys,zs, 0, GL_RED, GL_FLOAT, dat);
glTexImage3D(GL_TEXTURE_3D, 0, GL_RGBA8, size, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, pdata);
对于标量数据，我将使用第一个选项.还有更多格式没有被限制，只是尝试看看...
For scalar data I would use the first option. There are more formats that are not clamped just try and see...
我从未使用禁用钳位功能，但是在研究类似问题(不确定是否可行)时看到了这段代码:
I have never used the disabling of clamping feature but saw this code somewhere while researching similar issues (not sure if it works):
glClampColorARB(GL_CLAMP_VERTEX_COLOR_ARB, GL_FALSE);
glClampColorARB(GL_CLAMP_READ_COLOR_ARB, GL_FALSE);
glClampColorARB(GL_CLAMP_FRAGMENT_COLOR_ARB, GL_FALSE);
理论上讲，您可以使用任何纹理格式...
With that theoretically you could use any texture format...
要验证您可以使用此功能，
To verify you can use this:
我也看不到纹理集的任何参数.我希望像这样:
Also I do not see any parameters of the texture set. I would expect something like this:
glBindTexture(GL_TEXTURE_3D,txrvol);
glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_MODULATE);
避免插值弄乱您的数据以获得不精确的纹理坐标...
to avoid interpolation messing your data for non exact texture coordinates ...
这篇关于在片段着色器中访问3D数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
