How do you achieve Height based Opacity?

Development Rendering
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1

Hi,

I saw the tutorial about Location based Opacity and wonder if it would be possible to do something similar that is based upon a height, reltative to the character position. This could be used in a top down game to blend away ceilings etc. in buidlings when you enter them. How can this be done?

2

But how can I then drive the opacity with it? :smiley: Im really new to materials, so I need a little bit in depth advice. In code I would just compare the current height of the thingy in the material that you can get with get absolute height to the player height + a little offset and then just set the opacity to zero. But there seem to be no branches etc. in materials that blueprints have. Very confusing to me.

3

You can pass the player’s position in Z into the material via a scalar parameter.

Cheers,

Si

4

You could do something like the following:

Here I am passing in two parameters into the material.

Player Height = The player’s world position in Z.

Fade Height = The height over which you want to fade. At player’s height the opacity is 1, at Player’s Height + Fade Height it is 0.

I take the world position of the pixel, mask it to just B(aka Z), subtract the player height and clamp it between 0 and FadeHeight. So now the value is from 0 to FadeHeight. Everything below the player is at 0. Anything above PlayerHeight+FadeHeight is now FadeHeight. So dividing by FadeHeight gives us a value from 0 to 1. Take 1-that and we have a value from of 0 below the player, 1 at FadeHeight above the player and a smooth linear ramp between which we can feed into the opacity.

Hope that makes sense.

Cheers,

Si

8180-exampleheightfade.png
8180-exampleheightfade.png1268×568 105 KB

5

oops. Posted my comment as a new answer…doh

6

Hey, this works perfectly. Thank you kind sir :slight_smile:

7

Ok now one more problem I see with this. I can now basically cut off meshes visisbility by making them translucent. However, this leaves some very ugly looking side effects: You can now see inside the mesh, which doesnt look that good. Is there a way to maybe fill the cut off surface with a color or material, so it doesnt look as weird?

8

You could compare the height of the player vs each object in the Actor’s code or BP and feed the opacity for the whole object into the material directly as a parameter.