transparency questions

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Master of the Force
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transparency questions

Postby Anakin » Sun Jan 15, 2017 10:40 am

Hi,

just a few questions about the transparency:

1) what are the exact differences between additive transparency, hard-edged transparency, double-sided transparency, single-sided transparency?

2) Are there other ways to make something transparent??

3) If the material is transparent, it always uses the alpha channel of diffuse right? (what about specular + transparent? as far as i remember for low light settings, the spec map is copied to the alpha of the diffuse and for high light in the alpha of the bump/normal map)

4) is there any other way to make the material transparent?

5) do you think it would be ok if i don't differ between all the transparency variants and make it just transparent for all of this options in my viewer??

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Re: transparency questions

Postby Marth8880 » Mon Jan 16, 2017 3:17 am

Anakin wrote:1) what are the exact differences between additive transparency, hard-edged transparency, double-sided transparency, single-sided transparency?

Additive transparency can only be applied if the material has single-sided or double-sided transparency. Here's what it actually does: https://knowledge.autodesk.com/support/ ... 1-htm.html

Hard-edged transparency can only be applied if the material has single-sided or double-sided transparency. Here's what it actually does: https://docs.unrealengine.com/latest/IN ... tml#masked

Single-sided transparency is normal transparency, but polygons with it have what's called back-face culling. https://en.wikipedia.org/wiki/Back-face_culling

Double-sided transparency is the same as single-sided but it doesn't have the back-face culling.

It's worth noting that all polygons by default have back-face culling; the only ones that really don't are ones with double-sided transparency.

Anakin wrote:2) Are there other ways to make something transparent??

Like through an option file? I don't believe so, no. Although you can actually use vertex colors to drive the transparency values of a mesh by putting giving the mesh a Color At Vertices property in XSI and setting the material to use some-sided transparency with additive transparency, like I did by overlaying a layer of polygons over the floors and walls to get this neat frozen effect here:

Vertex colors in XSI:
Hidden/Spoiler:
Image

In-game:
Hidden/Spoiler:
Image

Diffuse texture's alpha channel:
Hidden/Spoiler:
Image


And to get this force field effect here:

Vertex colors in XSI:
Hidden/Spoiler:
Image

In-game:
Hidden/Spoiler:
Image

Diffuse texture's alpha channel:
Hidden/Spoiler:
Image


So as you can see, the color of a vertex drives that vertex's opacity, where the combined RGB value of the vertex's color = the vertex's opacity. (i.e. the brighter the vertex's color, the more opaque it'll be; and the darker the vertex's color, the less opaque it'll be)

With that said, this is done alongside the vertices' transparency being affected by the diffuse's alpha channel. It's done in two passes:

1. Diffuse alpha pass: Vertices with transparent material are affected by alpha channel in material's diffuse texture.
2. Vertex color pass: Vertex colors are applied to each vertex's opacity.

Anakin wrote:3) If the material is transparent, it always uses the alpha channel of diffuse right?

Correct.

Anakin wrote:what about specular + transparent?

I believe it still uses the diffuse texture's alpha, correct.

Anakin wrote:4) is there any other way to make the material transparent?

No.

Anakin wrote:5) do you think it would be ok if i don't differ between all the transparency variants and make it just transparent for all of this options in my viewer??

I recommend rendering additive transparency as whatever-sided transparency the material has. (so basically you should just ignore whether or not there's additive transparency - unless you want to implement the technique I mentioned in response to question 2)

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Re: transparency questions

Postby Anakin » Sun Feb 05, 2017 2:30 pm

What options are there to add normalmapping??

i found those:
Rendertype:
19
20
1b
1c

But what are the differences??

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