Need help with Render Targets - Urgent!

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ShellfishGames

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Posted: 16th Dec 2013 01:26 Edited at: 16th Dec 2013 01:29

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Hey!

I'm currently participating at Ludum Dare. The contest ends in 90 minutes, so some quick replies would be really helpful.

Everything worked fine the whole time but now suddenly a problem appeared that I can't solve, although it SHOULD be a matter of seconds.

I created a render target with Image Kit (ik create render target img,w,h). Now I want to set it to transparent. My first solution was to create an image with alpha = 0 on all pixels of the same size as my render target, and paste it onto it using ik paste image on image. This worked, but not anymore apparently. Hence I tried the ik set image channel command to set the alpha channel, but it doesn't do anything. I used it like this:

ik set image channel myRenderTarget, 0xFF000000, 0

No effect.

Furthermore there's the command "ik copy image to render target" listed in the help file, which sounds as if it could do what I want, but the command doesn't actually exist for some reason...

Any idea how I could achieve the desired effect of setting the alpha channel of a render target to 0 for all pixels?

Thanks in advance!

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mr Handy

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Posted: 16th Dec 2013 01:43 Edited at: 16th Dec 2013 01:45

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Write a shader for render target quad... if you have time.

edit:

Quote: "alpha channel of a render target to 0 for all pixels?"

Wait, what? Just hide the image...

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ShellfishGames

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Posted: 16th Dec 2013 01:49

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I want to "clear" the render target before pasting text into it. That's why I want to set the alpha value to 0 initially.

Quote: "Write a shader for render target quad... if you have time."

A shader can only be used for pasting the image though, and not to change it's data.. right?

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Sasuke

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Posted: 16th Dec 2013 01:54 Edited at: 16th Dec 2013 02:15

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The best way to do this would be to create a pixel shader for an IK effect and apply it to the render target. The pixel shader will handle the alpha!

EDIT: Example Attached

"Get in the Van!" - Van B

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ShellfishGames

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Posted: 16th Dec 2013 03:22

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Thanks for your help! Doesn't really solve the problem though, the way I see it. I probably didn't make the purpose of the whole thing clear enough: I want to change the actual data of the image, and not the way it is rendered.

Ludum Dare is now over and my game uploaded - I managed to fix the issue, somehow. I don't know why it works now, but as it turned out repeating the operations I already had implemented several times resulted in the desired behaviour.

In case anybody is interested in what exactly I did, here's a screenshot:

I use render targets for the text rendering. At first I print the text to a render target, then I use a sprite which uses this render target as source image to be able to draw the text into the level with any scale, coloring and rotation.

The level is actually 2D, I use a kind of displacement mapping to achieve the 3D effect. So the text sprites are simply drawn to another render target, which represents the whole ground. And that's basically it.

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Rudolpho

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Posted: 16th Dec 2013 10:11

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If it is an actual render target, just change the backdrop colour of the camera rendering it - setting it to 0x00000000 will indeed clear the alpha channel as well, provided you have ensured that the image actually has an alpha channel.
I don't know how Image Kit works though, so maybe this wouldn't be applicable.

Anyway, looks pretty nice

"Why do programmers get Halloween and Christmas mixed up?"

+ Code Snippet

Because Oct(31) = Dec(25)

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Sasuke

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Posted: 16th Dec 2013 13:06 Edited at: 16th Dec 2013 13:08

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Ahhh now I get what you were doing!

Damn, it's simple really.
1. You set all drawing commands to the render target
2. CLS 0 to clear it
3. Draw text - That's it!

Example:

+ Code Snippet

sync on : sync rate 60
set text size 50

ik create render target 1,256,256
make object cube 1,1
color object 1,rgb(128,128,128)

do
    r# = wrapvalue(r#+0.25)
    rotate object 1,r#,r#,0
    
    draw to image 1
        cls 0
        ink rgb(255,255,255),0
        center text 128,128-(text size()/2), str$(timer()/1000)
    draw to bitmap 0
    
    // or use sprite as you suggested
    paste image 1,screen width()/2-128,screen height()/2-128,1
    
    sync
loop

Good to see you achieved what you wanted and it's looking good

"Get in the Van!" - Van B

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