Alpha Blending with DynamicTexture (in a GUI)

[Draco18s]

	public void render(int left, int top, int width, int height) {
	Tessellator tessellator = Tessellator.instance;
	TextureManager renderEngine = FMLClientHandler.instance().getClient().getTextureManager();
	renderEngine.bindTexture(renderEngine.getDynamicTextureLocation("link", bufferedimage));
	GL11.glEnable(GL11.GL_BLEND);
	tessellator.startDrawingQuads();
	tessellator.addVertexWithUV((double)(left), (double)(128+top), 0.0D, 0.0D, 1.0D);
	tessellator.addVertexWithUV((double)(128 + left), (double)(128+top), 0.0D, 1.0D, 1.0D);
	tessellator.addVertexWithUV((double)(128 + left), (double)(top), 0.0D, 1.0D, 0.0D);
	tessellator.addVertexWithUV((double)(left), (double)(top), 0.0D, 0.0D, 0.0D);
	tessellator.draw();
	GL11.glDisable(GL11.GL_BLEND);
}

 

This works with one slight issue:

 

Any pixels in the bufferedimage with an alpha value lower than 26 (0x1A) aren't drawn at all.  Other values are drawn as expected with the appropriate amount of transparency.

 

How do I fix it?

[TheGreyGhost]

Hi

 

Try

 

        GL11.glDisable(GL11.GL_ALPHA_TEST);

 

The Alpha test threshold is set in a few places

eg Minecraft.loadScreen() and Minecraft.startGame();

 

        GL11.glAlphaFunc(GL11.GL_GREATER, 0.1F);

 

(0.1F being 0.1 * 256 = 26)

 

-TGG

 

[Draco18s]

Hi

 

Try

 

        GL11.glDisable(GL11.GL_ALPHA_TEST);

 

Ah ha!

Fantastic.  I knew something like that was floating around somewhere, but I had no idea where to look or what to look for (I don't typically deal with OGL).

[TheGreyGhost]

Keen, glad it worked.

 

only stumbled over it myself by accident when trying to figure out how block transparency works.

 

-TGG

[Draco18s]

I haven't actually tried it yet, but I'm pretty sure that's it.

 

Edit:

Got a moment to drop a glDisable in.  Works perfectly.

[gcewing]

You might also want to make sure the blending function is set appropriately, e.g.

 

GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

 

I just fixed a bug in SG Craft that was due to failing to do this.

[Draco18s]

You might also want to make sure the blending function is set appropriately, e.g.

 

GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

 

I had already, actually.