[SOLVED] Multiple polygons not being drawn to a canvas

[CrackedP0t]

With this LÖVE file, only the last polygon is drawn.

Why is that, and what can I do to draw all of them to the same canvas?

main.lua for your convenience:

Code: Select all

function love.load()
	canvas = love.graphics.newCanvas(100, 100 * math.sin(1/3 * math.pi))
end

function love.draw()	
	love.graphics.setCanvas(canvas)
	canvas:clear()
	
	local drawWidth = canvas:getWidth()
	local drawHeight = canvas:getHeight()
	
	local middleY = 3/5
	
	love.graphics.setColor(255, 0, 0)
	love.graphics.polygon("fill",
		0.5 * drawWidth, middleY * drawHeight,
		1.0 * drawWidth, 1.0 * drawHeight,
		0.0 * drawWidth, 1.0 * drawHeight)
	
	love.graphics.setColor(0, 255, 0)
	love.graphics.polygon("fill",
		0.5 * drawWidth, middleY * drawHeight,
		0.5 * drawWidth, 0.0 * drawHeight,
		1.0 * drawWidth, 1.0 * drawHeight)
	
	love.graphics.setColor(0, 0, 255)
	love.graphics.polygon("fill",
		0.5 * drawWidth, middleY * drawHeight,
		0.5 * drawWidth, 0.0 * drawHeight,
		0.0 * drawWidth, 1.0 * drawHeight)
		
	love.graphics.setCanvas()
	
	love.graphics.draw(canvas)
end

[bartbes]

They're all drawn, they're just drawn on top of each other.

[CrackedP0t]

They're all drawn, they're just drawn on top of each other.

How can I make them all visible?

[bartbes]

They.. kind of are? They're all just solid polygons exactly overlapping. What would you want to have happen?

[bobbyjones]

CrackedP0t move one of them around

[CrackedP0t]

They.. kind of are? They're all just solid polygons exactly overlapping. What would you want to have happen?

They're not, though. If you comment out the blue polygon, you'll see the green one to the right. Also, if you draw them to the normal screen rather than a canvas, they draw properly.

[Nixola]

Set the color to white before drawing the canvas.

[Positive07]

Well you are doing something like this:

Code: Select all

love.graphics.setColor(255,0,0)
love.graphics.rectangle(100,100,100,100)
love.graphics.setColor(0,255,0)
love.graphics.rectangle(100,100,100,100)

What color would the square be?

Check the snippet you posted, the points of the polygons are the same for all of them! If you dont believe me, make the alpha value of each setColor equal to 50.

This is true unless the code you attached in the code block is different to that in the .love file (which I cant test because I'm not in Linux at the moment)

[Nixola]

As I said, the issue is you're not setting the color back to white before drawing the canvas to your screen. The polygons, at least inside the .love file, don't have the same points and setting the color before drawing the canvas actually works.
EDIT: they're not drawn in the same position in the code he posted either.
That said, you should only draw to the canvas just once, not every frame, or there is really no point in using one.

[zorg]

That said, you should only draw to the canvas just once, not every frame, or there is really no point in using one.

I kinda disagree; i mean, i can use 3 canvases, and update one once every xth frame, one every yth frame, and one every frame, granted i have a reason to. I'm just saying, canvases can be useful when you are redrawing them every frame as well. (Only thing coming to my mind are layers for background and objects, though that can be accomplished with spritebatches as well...)
woo 2*10^2th post