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Quat

Member Since 15 Sep 2003
Offline Last Active Jul 08 2014 05:10 PM
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Posts I've Made

In Topic: Point density

25 April 2014 - 04:41 PM


This is a horrible way to write it: "dL->0" means nothing.

 

How is dL->0 different from h->0.  My dL is the same as your h.

 


If you have a function M such that M(x) tells you how much mass there is to the left of x, then the mass density is the derivative of M.

lim_{h->0) (M(x+h) - M(x)) / h

 

This works because then M(x+h) - M(x) tells you the mass in the "cell" over h. 

 

What is the generalization to 2D area densities--M(x,y) where there is not a "left" or "right"?


In Topic: Get a formula from a graph

05 February 2014 - 11:44 AM

I could be wrong, but I think something like cubic spline interpolation might be better than nth degree polynomial.  A polynomial can get some pretty wild oscillations to fit the data points. 


In Topic: Tone Mapping Washing out Detail

03 February 2014 - 06:42 PM

In that screen, they are all LDR values.  I'm not really sure how to add HDR lights to my outdoor day scenes because I am just using the sun directional light, and it will affect pixels equally, so I'm not sure there is an advantage to bumping my sun to HDR values. 

 

For my night scenes, I do have HDR lights and thus HDR values.  Maybe I should just enable tonemapping at night, but I was hoping I could get some uniform solution. 

 

I am remapping like this:

 

float pixelLuminance = CalcLuminance(exposedColor);    
float toneMappedLuminance = pixelLuminance / (pixelLuminance + 1);

float3 toneMappedColor = (toneMappedLuminance / pixelLuminance) * exposedColor;


In Topic: sRGB formats

30 January 2014 - 03:09 PM

Okay I think I am getting it.  Since I am using a deferred renderer, my diffuse albedo buffer is 8-bit, whereas my light accumulation buffer is 16-bit.  So should my I actually be making my albedo render target sRGB since it stores 8-bit?  Then convert to linear for the lighting pass?


In Topic: HDR Light Values

27 January 2014 - 01:43 PM


Generally, intensity values like that are unitless unless you specifically work out some scale for them. A fair number of archviz renderers do so in order for them to work nicely with measured IES light profiles. There isn't a *formal* standard with games/the DCC packages used to create their assets, though, as physically-based rendering is just starting to catch on these days.

 

So is informal game approach just to take some "standard light" like a typical room light bulb and give it some arbitrary light intensity, say (1, 1, 1), and then define other lights relative to that?  Like if a light should be 4X brighter than a typcal room light bulb, then it will have (4, 4, 4)?

 


You likely will see better results moving over to a simple area light model, though, as point lights are physically impossible. This would also give you a more sensible attenuation model 'for free.'

 

Do you have a link describing such a "simple area light model"?  I thought area lights were mainly for soft shadows, but too expensive to simulate in real-time.


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