Help with Alpha transparency in geometry instancing

[estebanarellano]

Hi there! Relatively new to TouchDesigner so would really appreciate some support here with transparency. I have set up a Geometry instancing rectangles along a line SOP. Each of these rectangles have a Phong MAT that is connected to a 3D Texture to display a video at various time frames. I am trying to setup an alpha effect so that the rectangles grow in transparency as they move along the z-axis. I’ve tried creating an alpha channel from a SOP to CHOP and then putting this into the Geometry color mode but that doesn’t seem to work. I have read the Transparency Wiki and am still struggling to understand how to achieve this effect. Attached photos for reference.

Thank you so much!

[estebanarellano]

HEREWEGO.7.toe (39.9 KB)

[flowb]

Hi,

I found setting the Color Mode to ‘Multiply’ in the instancing panel made the behavior more as expected.

Since you want to affect an existing alpha channel, multiplying the instanced value by the input alpha channel makes the values ‘stack’. The setting you had (‘Replace’) just overwrites the values.

Setting ‘Discard Pixels based on Alpha’ in the Phong MAT lets you see the background layers through the other instances:

HEREWEGO_fm.toe (12.8 KB)