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gmax Community and Support : Gamepak: Flight Sim 2002 : Alpha channel transparency

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brites

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12 Posts

Alpha channel transparency

Posted 31-Mar-2006 7:53 AM

Hello again

I've maid a bmp file for windows and created a alpha channel for transparency... I can only obtain full transparency vs null transparency... I've tried do change the alpha c to a RGB of 80-110 grey scale but it still doesn't give the semi-transperency effect I want... need tips...

Fr. Bill

Advanced Poster

737 Posts

RE: Alpha channel transparency

Posted 31-Mar-2006 9:40 AM

Did you use DXT3 w/alpha for your bitmap? DXT1 will NOT work!

Did you remember to add the _t suffix to the texture name? myTexture_t.bmp

Did you remember to enable "Has Transparency" in MakeMDL.exe?

brites

Poster

12 Posts

RE: Alpha channel transparency

Posted 31-Mar-2006 10:42 AM
Modified by brites On 31-Mar-2006 10:46 AM

the only thing thing i didn't make is DXT3 i've been using DXT1 i´m going to try it out

thanks...

brites

Poster

12 Posts

RE: Alpha channel transparency

Posted 31-Mar-2006 10:58 AM

After your reply I went surfing and found this small resume of texture formats... It's always good to know more...

RGBA8 – 32-bit RGB with Alpha

This is the simplest "raw" format. Each pixel is represented by one byte each for the red, green, blue, and alpha channels. This format allows for the widest possible range of color and alpha information, but at the expense of very large image size in memory and on disk (a 512x512 texture takes up 1MB of memory). For this reason, it is recommended that this format not be used unless absolutely necessary. (Import/export formats: BMP, PCX, TGA, UPT)

DXT1 – DXT Compressed, opaque/one-bit alpha

The most compact format for texture data supported by the Unreal Engine. DXT1 can store full-color textures with a total image size of 4 bits per pixel (half that of P8), but does suffer from some loss of image quality. DXT1 textures have either no transparency at all or just a single transparent color.(Import/export formats: DDS)

DXT3 – DXT Compressed, linear alpha

DXT3 textures offer the same image quality as DXT1, but add sixteen-level (4-bit) alpha information for each pixel, making this format good for textures with sharply contrasting translucent/opaque areas. This does, however, have the drawback of doubling the image size (to 8 bits per pixel) over DXT1. (Import/export formats: DDS)

DXT5 – DXT Compressed, interpolated alpha

DXT5 is another variation of DXT1 with additional alpha information. Like DXT3, DXT5 features an image size of 8 bits per pixel (twice that of DXT1), however DXT5 uses an interpolated alpha scheme which allows for smoother transitions in alpha values than DXT3 (but has less precision for sharp changes in alpha). (Import/export formats: DDS)

P8 – 8-bit Palletized

P8 textures store each pixel as an index into a table of 256 possible colors (similar to the GIF file format). P8 textures can also optionally have 1-bit (on or off) transparency information, which is done by considering the color index 0 to represent "transparent". P8 is one quarter the size of RGBA8, while potentially offering substantially better color representation of DXT, often offering a good compromise in the middle of the size/quality spectrum. (Import/export formats: BMP, PCX)

??? – 8-bit Palletized with Alpha

A special variation on P8 is the alpha-palettized format where each one of the 256, 32-bit palette entries holds an RGBA value instead of RGB. This is mostly relevant only for the PSX2 builds of the engine; given the PSX2 architecture, it's the most efficient form of storing a variable-alpha texture. The catch is that having to put variable alpha in a palette diminishes the already limited color variety available; but in many cases this isn't significant, and several font-and user interface textures have been created this way. (Import/export formats: Special form of BMP?)

G16 – 16-bit Grayscale

Primarily used for terrain heightmaps, G16 textures offer 65536 levels of gray, providing greatly increased precision of grayscale information for those rare cases where it is needed. Most external graphics applications are not able to handle 16-bit grayscale information, however, so manipulating G16 images outside of UnrealEd may require specialized software, such as G16ed. RGBA8 and P8 textures can be converted to G16 in UnrealEd by setting the texture as a heightmap for a terrain, and once it's visible in the Terrain Mode window, right-clicking on its thumbnail and selecting "convert to G16" from the pop-up menu. (Import/export formats: BMP Note: The G16 "BMP" format is not actually a valid BMP file, and will not work correctly with most programs)

Katahu314

New Poster

10 Posts

From Katahu314

Posted 22-Apr-2006 12:12 AM

When the suffix "*_t" (exclude the quotations) is appened to the end of a texture name, FS will render the texture with the applied alpha as a reflection. If you "exclude" the suffix altogether, the alpha will then have a transparent effect as this tells FS that the texture with the alpha is "not" being used for reflections.

You see what I'm saying? I learned this from experience since I was learning to make reflections instead of tranparencies. It took me a while to realize that (besides the DXT format thing) the suffix dictates whether it becomes a reflective texture or a transparent texture.

scenerydesign

Poster

75 Posts

RE: From Katahu314

Posted 23-Apr-2006 2:19 PM

Just out of curiosity, is it only the _t suffix that tells FS to render it as reflection? I always thought it was because you defined the bitmap as the specular map and that the name does not matter at all.

Arno
www.scenerydesign.org


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