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# spotlight shadow effect

Posts: 33Member, BASIC

Hello, I am making a game involving sweeping spotlight. I have several actors move around and I want my actors block the light and create a shadow behind them. The shape of the shadow should depends on the angle between the light and the actor. I don't know how to realize this. I attached an image to demonstrate this. Thank you.

Go Download "Sub Run" in App Store.

• Posts: 33Member, BASIC

I know I can spawn a "shadow" actor and constrain its position related to the blue actors, but how can I make the shape of the shadow change when my light is shooting from a different angle.

Go Download "Sub Run" in App Store.

• London, UK.Posts: 12,822Member
edited November 2015

@liux2355 said:
I know I can spawn a "shadow" actor and constrain its position related to the blue actors, but how can I make the shape of the shadow change when my light is shooting from a different angle.

You could replicate in the opposite direction (= from main actor to light source) using the Replicate behaviour . . . . hold on, I'll make a quick demo of what I mean . . . .

. . . . .

EDIT: demo attached/ drag the light source around (smaller pale yellow square).

• Posts: 33Member, BASIC

@Socks said:

@liux2355 said:
I know I can spawn a "shadow" actor and constrain its position related to the blue actors, but how can I make the shape of the shadow change when my light is shooting from a different angle.

You could replicate in the opposite direction (= from main actor to light source) using the Replicate behaviour . . . . hold on, I'll make a quick demo of what I mean . . . .

. . . . .

EDIT: demo attached/ drag the light source around (smaller pale yellow square).

It works great but in my case, I have a fixed light source and my actor is spawned randomly and move around, then this method can not work. What should I do if I want to move the actor and shadow instead of light. Thanks.

Go Download "Sub Run" in App Store.

• London, UK.Posts: 12,822Member
edited November 2015

@liux2355 said:
It works great but in my case, I have a fixed light source and my actor is spawned randomly and move around, then this method can not work.

It was just a demo file to show the concept of using Replicate to make the shadow, you are not stuck with a moving light source and a static actor, you can set it up any way you like.

If you want the actor to move with the shadow then constrain the actor's x and y position to the shadow's x and y position.

• Posts: 33Member, BASIC

@Socks said:

@liux2355 said:
It works great but in my case, I have a fixed light source and my actor is spawned randomly and move around, then this method can not work.

I was just a demo file to show the concept of using Replicate to make the shadow, you are not stuck with a moving light source and a static actor, you can set it up any way you like.

If you want the actor to move with the shadow then constrain the actor's x and y position to the shadows x and y position.

I've been working on it for some time and it works pretty well. Thank you!

Go Download "Sub Run" in App Store.