Hi,
Can anyone explain to me how to go about using HDR in panda3d?
I understand the concept of HDR but I am lost as to how to go about implementing it in panda. I have searched the forums and played around with lightramps and other code, but I just cant make anything happen.
thanks.
It’s pretty easy. You need to apply a LightRampAttrib:
# Choose whichever gives the best effect
#node.setAttrib(LightRampAttrib.makeHdr0())
node.setAttrib(LightRampAttrib.makeHdr1())
#node.setAttrib(LightRampAttrib.makeHdr2())
node.setShaderAuto()HDR looks best in combination with bloom.
Any example images of HDR rendering ?
I’m trying to get a feel for how HDR works with custom shaders.
I understand that if I set it, let’s say:
node.setAttrib(LightRampAttrib.makeHdr0())
then in GLSL I can, for example, multiply p3d_Color.rgb by let’s say 10.0 and at the end tone-mapping will adjust it to the range from 0.0 to 1.0. Meanwhile, nothing like that happens. Basically, it’s as if HDR doesn’t work at all. In the sense that I boost the RGB components in the shader and as soon as they go above 1.0, they become saturated in the old way and I have everything overexposed to white.
What am I doing wrong?
If you’re using a custom shader, then I presume that the auto-shader isn’t active–in which case I daresay that Panda’s tone-mapping shader isn’t in effect. (As I imagine that any tone-mapping done by Panda is being done by the auto-shader.)
I think, then, that the thing to do is likely to implement the tone-mapping on your end, either in the shader mentioned above or in a post-process shader of your own.
Thank you for your answer. I have no problem to implement tone mapping in the shader myself. Unfortunately, it seems to me that this HDR just doesn’t work for me.
Let’s take an example.
Here is the Panda3D Python code:
from direct.filter.FilterManager import FilterManager
from direct.showbase.ShowBase import ShowBase
from panda3d.core import (
LightRampAttrib,
ColorBlendAttrib,
Texture,
Shader,
loadPrcFileData,
)
loadPrcFileData("", "gl-version 4 1")
base = ShowBase()
base.setBackgroundColor(0.75, 0.75, 0.75)
# noinspection PyArgumentList
base.render.setAttrib(LightRampAttrib.makeHdr0())
# noinspection PyArgumentList
base.render.setAttrib(ColorBlendAttrib.make(ColorBlendAttrib.MAdd))
model = base.loader.loadModel("ripple")
model.reparentTo(base.render)
model.setPos(0, 2, 0)
manager = FilterManager(base.win, base.cam)
tex = Texture()
quad = manager.renderSceneInto(colortex=tex)
# noinspection PyArgumentList
quad.setShader(
Shader.load(
Shader.SL_GLSL,
vertex="basic.vert",
fragment="basic.frag",
)
)
quad.setShaderInput("tex", tex)
base.run()
Here is the vertex shader code in GLSL:
#version 410
uniform mat4 p3d_ModelViewProjectionMatrix;
in vec4 p3d_Vertex;
void main() {
gl_Position = p3d_ModelViewProjectionMatrix * p3d_Vertex;
}
Here is the shader fragment code in GLSL:
#version 410
uniform sampler2D tex;
out vec4 p3d_FragColor;
void main() {
p3d_FragColor = texture(tex, gl_FragCoord.xy / textureSize(tex, 0));
p3d_FragColor.rgb -= 0.75;
}
Now let me explain what’s going on here.
I’m loading one of the standard Panda3D objects, “ripple”. I place the object on a fairly light background: (0.75, 0.75, 0.75). Normally it would look like this:
But this time, what’s more, I render the object in additive mode, i.e. the pixel brightness of the “ripple” itself is added to the already bright background. Naturally, a large part of the pixels are overexposed and looks like this:
Well, yes, but we supposedly have HDR turned on, i.e. we have inactive upper clamping, which means that pixels can take values with > 1.0 components. So if I then add a full-screen quad, which will act as a filter, and in this filter I subtract 0.75 from each component, I would expect the background to become black (because 0.75 - 0.75 = 0.0), and the object “ripple” will have the original colors. However, this is not quite what happens:
Yes, the background becomes black (with HDR not needed here, of course, because we were within the scale), but the colors of the object are distorted. So clearly, somewhere along the way, there was an upper clamping at the value of 1.0, despite the HDR mode being enabled for the entire scene (for base.render).
Where am I making a mistake?
Hmm… You’re right.
And I’m afraid that even after some tinkering on my end, I’m not managing to make it work. :/
I’m really not sure of where the problem is–sorry! Hopefully another forum-member will know better!
Closed the thread to keep discussion focused; the current way of doing HDR is not via LightRampAttrib but is described here:
