Improved Alpha channel and Transparency for exporting JSON material

[knn217]

_Images plugged into "Principled BSDF" 's Alpha will combine with Images at BaseColor as the alpha channel (Since Ogre use 1 image for both color and alpha).

_More options for texture's BlendBlock, controlled by Blender's 3 Blend modes:

• Alpha Clip = just Blend Type: REPLACE
• Alpha Blend = a BlendBlock with custom setting, very transparent
• Alpha Hashed = a BlendBlock with custom setting but less transparent than Alpha Blend

_There was also plan for supporting other texture nodes aside from image, but I couldn't find a way to get the node's color matrices

Edit: The image texture needs to be plugged in the "Value" input a "map range" node and then connect "Result" to the Alpha channel (like how metallic and roughness texture is plugged in through a "separate colore" node).
This is so that "Map range" 's "To Max" value can be used to modify the Transparency strength, which is determined by ["Transparency"]["value"] in the .material.json file.

Here's what my setup look like for combining Base Color texture and Alpha texture:

And here are the results for the 3 Blend mode setting:
*Alpha Clip

*Alpha Blend

*Alpha Hashed

Alpha Blend is very hard to see, but is definitely there

• Also note that these Blend modes just decide the "style" of Blending, not the Transparent strength even if they look like they do. The Transparent strength is decided by the "To Max" value of "Map range node". These 3 modes also output the same combined texture.

[paroj]

Here's what my setup look like for combining Base Color texture and Alpha texture:

I dont think there is much value for supporting a separate alpha texture. We should rather assume that the alpha channel of the base texture is used, if present.

[paroj]

* Alpha Clip = just Blend Type: REPLACE

* Alpha Blend = a BlendBlock with custom setting, very transparent

* Alpha Hashed =  a BlendBlock with custom setting but less transparent than Alpha Blend

this does not make sense. Alpha clip should map to alpha_rejection or whatever it is called in ogre next.

Alpha Hashed must be equal to Alpha Blend.

[knn217]

Here's what my setup look like for combining Base Color texture and Alpha texture:

I dont think there is much value for supporting a separate alpha texture. We should rather assume that the alpha channel of the base texture is used, if present.

Yes, the code also support this!
If you plugged the Alpha channel of Base Color texture into Map Range, it will also work:

The "Map Range" node is required since the code uses this to determine ["Transparency"]["value"], this was originally determined by the alpha channel's default value of Principled BSDF, but it is overwritten if plugged in so I changed this to "Map Range" so that the effects are more in sync between Blender and Ogre.

[knn217]

* Alpha Clip = just Blend Type: REPLACE

* Alpha Blend = a BlendBlock with custom setting, very transparent

* Alpha Hashed =  a BlendBlock with custom setting but less transparent than Alpha Blend

this does not make sense. Alpha clip should map to alpha_rejection or whatever it is called in ogre next.

Alpha Hashed must be equal to Alpha Blend.

Yes, I think it is "alpha_test" in Ogre-next.
You are right about Alpha clip, it actually doesn't need a BlendBlock, I just need to set "Transparency" mode to "None" but I was copy pasting that code section since it have the same effect, but yeah this might confuse the user, I'll change it back.

About Alpha Hashed, I also thought its basically the same as Alpha Blend, so I made it have a different Blend type to make use of this slot. I can change it back to be the same as Alpha Blend tho.

[knn217]

I also added in a feature that can combine alpha texture with "base color" value if there's no diffuse texture, so a setup like this:

will give you this:

The combined texture can be detailed (depends on the Alpha texture) but didn't look very good, so I combined the effects from metallic, roughness and normals. Here's what it looks like without these effects:

This is a convenient way to create assets for users since all you really need is an image to use as Alpha texture, which doesn't even need the alpha channel since black/white image can use the color channel instead. So all the user need is 1 image, like so:

[paroj]

sorry for not being clear previously: I think that we explicitly should not handle the cases that you are currently implementing, particularly:

I also added in a feature that can combine alpha texture with "base color" value if there's no diffuse texture, so a setup like this:

and

The "Map Range" node is required since the code uses this to determine ["Transparency"]["value"]

this complicates code that needs to be maintained moving forward and is only specific to one usecase. This should rather be offloaded to the user before the exporter is run.

Also note, that imagick presence is optional so you cannot rely on being able to use it for fixing things. The export should succeed even without imagick.

[knn217]

OK, so only remove the alpha texture code right?

[knn217]

Changes were applied, please check to see if I missed anything.