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methods for controling screen brightness


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#1 Norman Barrows   Crossbones+   -  Reputation: 1966

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Posted 07 April 2013 - 10:48 AM

what are some methods for controlling screen brightness?

 

i'm using DX9.0c fixed function pipeline.

 

all lights are diffuse only, no ambient, and 1.0,1.0,1.0 specular.

 

world ambient is 255,255,255

 

so ambient, specular and emissive are controlled by materials only.

 

all materials have some diffuse.

 

to increase brightness, i multiply ambient, diffuse, specular, and emissive in all materials by a "brightness multiplier" of 1x to 50x.

 

what other methods are there?

 

gamma ramp? this seems to be geared more towards color correction.

 

 

 


Norm Barrows

Rockland Software Productions

"Building PC games since 1988"

 

rocklandsoftware.net

 


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#2 Juliean   GDNet+   -  Reputation: 2331

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Posted 07 April 2013 - 11:54 AM

Did you try to use an ambient light that you could scale from approximately 0.0f to 1.0f?



#3 Norman Barrows   Crossbones+   -  Reputation: 1966

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Posted 07 April 2013 - 05:27 PM

Did you try to use an ambient light that you could scale from approximately 0.0f to 1.0f?

 

 

haven't tried that one yet. i'll give it  a shot. Thanks!


Norm Barrows

Rockland Software Productions

"Building PC games since 1988"

 

rocklandsoftware.net

 


#4 Adam_42   Crossbones+   -  Reputation: 2418

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Posted 07 April 2013 - 05:36 PM

Here's a few options:

 

1. IDirect3DDevice9::SetGammaRamp(). No good in windowed mode, and theoretically some cards may not support it, but it's easy to code and flexible.

 

2. Use a shader to post process the output. Works in Windowed mode. Has some performance cost to it, although not much if you can combine it with other post processing.

 

3. Render the scene bright and draw a semi transparent black quad over the top to make it darker. This works fine for a fade out, but isn't as flexible as the previous options, and has a performance cost similar to #2.

 

4. Adjust the brightness of every single object you render, by modifying the material settings. Tricky to get this looking right, and not good for performance.



#5 mhagain   Crossbones+   -  Reputation: 7565

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Posted 07 April 2013 - 05:50 PM

Another method (variant on Adam_42's option 2) that will work with the fixed pipeline is to use render to texture and a 4 x modulate texture stage state when drawing back the full-screen quad.  You can modulate either with a color attribute in your FVF or vertex declaration, or with a constant color (D3DTSS_CONSTANT), but in both cases a color of 0.25 (D3DCOLOR_XRGB (64, 64, 64)) would represent normal brightness and obviously lower is darker, higher is brighter.  That would only give you a 0x to 4x range (although you would be able to get up to 8x with some (ab)use of blend states), obviously, but it's the best I can think of that doesn't involve diving into shaders.


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#6 Norman Barrows   Crossbones+   -  Reputation: 1966

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Posted 08 April 2013 - 01:15 PM

4. Adjust the brightness of every single object you render, by modifying the material settings. Tricky to get this looking right, and not good for performance.

 

this is basically the approach i'm taking.

 

but unlike the traditional directx way of doing things, i keep meshes, textures, and materials separate and interchangeable. so i only use a d3dxmesh as a convenient way to store a vertex and index buffer, and don't store any texture or material info in the mesh. therefore, i have a global array of materials used for everything. the game uses 7 different materials at the moment. there's a routine that sets all the materials to their default values (normal brightness). when the user changes the brightness level, i simply reset the materials to default, then multiply their values by the new brightness level. the game then runs as usual, until the brightness is changed again. so i never have to do anything ugly like change the material in a d3dxmesh before i draw it, then change it back, every time i draw it.  i just scale the material values once when the player changes brightness, and i'm done. one of the plusses of this method is no additional lights required. i had experimented with additional diffuse lighting, even at out of bounds high levels, with no success. this led to the conclusion that what was required was not more light, but brighter objects.

 

the effect is not bad, scaling should not be linear though, changes are too coarse at first, and too fine near the end.  looks like specular should not be increased, or not as much. but now i know how Oblivion gets all those nice looking unrealistically shiny rocks. too much specular seems to enhance texture depth, almost like bump mapping. looks cool. unrealistic, but cool.


Norm Barrows

Rockland Software Productions

"Building PC games since 1988"

 

rocklandsoftware.net

 


#7 Juliean   GDNet+   -  Reputation: 2331

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Posted 08 April 2013 - 01:27 PM

the effect is not bad, scaling should not be linear though, changes are too coarse at first, and too fine near the end. looks like specular should not be increased, or not as much. but now i know how Oblivion gets all those nice looking unrealistically shiny rocks. too much specular seems to enhance texture depth, almost like bump mapping. looks cool. unrealistic, but cool.

 

Oblivion uses a combination of HDR and blooming to achieve those, so withem them (or similar techniques) this is not really possible.



#8 Norman Barrows   Crossbones+   -  Reputation: 1966

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Posted 08 April 2013 - 06:21 PM

i takes it that before shader tricks, gamma was a common method?


Norm Barrows

Rockland Software Productions

"Building PC games since 1988"

 

rocklandsoftware.net

 





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