Share a Shader!

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girng
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Re: Share a Shader!

Post by girng » Fri Sep 07, 2018 7:31 pm

I have a shader that works in Godot, can I still use it in love2d?

It basically just creates an outline around a sprite (of a certain color)

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wazoowazoo
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Re: Share a Shader!

Post by wazoowazoo » Tue Oct 30, 2018 1:13 pm

I have created a basic water shader, hope you will like it.
water.love
(230.82 KiB) Downloaded 291 times
I am currently working on reflection.

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wazoowazoo
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Re: Share a Shader!

Post by wazoowazoo » Wed Nov 07, 2018 12:07 pm

I have created another shader, this time a fractal. Left mouse button is to place a fractal, backspace to reset graphics, return (enter) to reset frames, space to pause/unpause and scrolling makes it evolve faster or slower. I hope you will have fun playing around with it ! :)

Fractal.love
(1.25 KiB) Downloaded 192 times

Here's a preview:
Fractal.png
Fractal.png (228.97 KiB) Viewed 4444 times

trabitboy
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Re: Share a Shader!

Post by trabitboy » Wed Sep 11, 2019 9:54 pm

Hi!

I am currently porting a paint tool to love2d because:
lua is awesome and
love2d is awesome and supports shaders

I am looking for an example of a love 2d shader with 2 textures as input;
scenario:
I want to erase using the gpu,
meaning I want to have painting canvas and an eraser texture as an input, blitting to another canvas as output .

I climbed back this thread quite far but I could find no multiple inputs shader ?

Thanks for any help !

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Sasha264
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Re: Share a Shader!

Post by Sasha264 » Thu Sep 12, 2019 10:18 am

trabitboy,
Hi! :awesome:

To pass 2 or more images (canvases, textures) to the shader you can declare they inside shader code using extern directive.
And after that but before using this shader you need to send this texture to a shader using shader:send(...) method https://love2d.org/wiki/Shader:send

Note, that you can ignore "default" texture from the second argument from effect(...) function at all and use only yours named textures, declared using extern Image [name] :cool:

Here is some possible "erasing" shader (but I don't know exact details so it can be adjusted):

Code: Select all

local shader

-- call once per program run
function InitShader()
	local pixelcode = [[
		extern vec2 shift;
		extern Image eraser;

		vec4 effect(vec4 color, Image texture, vec2 tc, vec2 sc)
		{
			vec4 texturePixel = Texel(texture, tc);
			vec4 eraserPixel = Texel(texture, tc + shift);
			texturePixel.a = texturePixel.a * (1.0f - eraserPixel.a);
			return texturePixel;
		}
	]]

	shader = love.graphics.newShader(pixelcode)
end

-- call once for change eraser texture
function SetEraserTexture(eraser)
	shader:send("eraser", eraser)
end

-- call every time you want to move eraser, i.e. every frame
function SetEraserShift(shift)
	shader:send("shift", shift)
end
BTW, I suppose for this question a separate thread will be more appropriate :3

trabitboy
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Re: Share a Shader!

Post by trabitboy » Fri Sep 13, 2019 12:48 am

well thanks Sasha264, that is very helpful :awesome:

trabitboy
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Re: Share a Shader!

Post by trabitboy » Mon Sep 16, 2019 4:13 pm

Here is my example inspired from Sasha264 ,
but offset calculation is not correct in my case .
( getting pretty close )

EDIT: corrected, was not offseting on tex coords but cvs coords

Code: Select all


--this shader substracts alpha of the eraser brush
--offset calculation still incorrect

function love.load()

	offset={}
	offset.x=400.0
	offset.y=400.0

	circle=love.graphics.newImage('circle.png')

	cvs1=love.graphics.newCanvas(640,480)
	love.graphics.setCanvas(cvs1)
	--first canvas is filled with redmod
	love.graphics.clear(1.0,0.0,0.0,1.0)

	--the canvas holding the real image data
	curcvs=cvs1

	
	cvs2=love.graphics.newCanvas(640,480)
	love.graphics.setCanvas(cvs2)
	love.graphics.clear(0.0,0.0,0.0,0.0)

	backcvs=cvs2 -- the back buffer the frag shader will render to

	love.graphics.setCanvas()

	local pixelcode=[[
		//second is the eraser
		extern Image second;
		extern float cvsw;
		extern float brshw;
		extern float cvsh;
		extern float brshh;
		extern float offx;//pixels
		extern float offy;//pixels

		vec4 effect(vec4 color,Image texture,vec2 tc,vec2 sc){
			
			
			float pxw=1.0 / brshw;
			float pxh=1.0/brshh;
			
			
			vec4 texturePixel=Texel(texture,tc);
			
			
			float tcx = tc.x*cvsw/brshw-offx*pxw;
			if (tcx>1.0 || tcx<0.0 ){
				return texturePixel;
			}
			float tcy = tc.y*cvsh/brshh-offy*pxh;
			if (tcy>1.0 || tcy<0.0){
				return texturePixel;
			}
			vec2 rtc=vec2(tcx,tcy);
			
			vec4 secondPixel=Texel(second,rtc);
			
				vec4 ret=texturePixel ;
				ret.a=ret.a-secondPixel.a;
				return ret;
			
		}
	]]
	
	shader=love.graphics.newShader(pixelcode)

	shader:send("second",circle)
	shader:send("cvsw",640.0)
	shader:send("brshw",64.0)
	shader:send("cvsh",480.0)
	shader:send("brshh",64.0)
	shader:send("offx",offset.x)
	shader:send("offy",offset.y)

	--test erase from curcvs to backcvs
	love.graphics.setCanvas(backcvs)
	love.graphics.setShader(shader)
	love.graphics.draw(curcvs)
	love.graphics.setShader()
	love.graphics.setCanvas()

end


function love.draw()

	love.graphics.draw(backcvs)
	love.graphics.print('eraser shader test')


end

Attachments
love2dshadertests.zip
(4.17 KiB) Downloaded 67 times

aoi_saboten
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Re: Share a Shader!

Post by aoi_saboten » Wed Oct 02, 2019 6:13 pm

Hello guys.

Can you look to that CRT-shader used here --> https://github.com/Akylzhan/CRT-shader

Is it possible to make that effect much better? I am worried about color palette since it is very colorful and about display boundaries, can I make it smoother?

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