Trouble with Render Targets

[thehankinator]

I am trying to make a split screen effect.

 

For some reason, it appears that the it only renders once to the texture, never updates. Is this a known limitation? If I disable the render targets the FPSPlayer behaves normally so I think everything is in order there.

 

I've created 2 textures, black.tex and green.tex. Then, I assigned a texture to each camera. Inside Main.lua I've done the following:

 

Before the while loop:

local player1view = Texture:Load("Materials/RenderTargets/black.tex")
local player2view = Texture:Load("Materials/RenderTargets/green.tex")

 

 

After world:Render()

context:SetColor(1,1,1)
context:DrawImage(player1view, 0, 0, context:GetWidth(), context:GetHeight()/2)
context:DrawImage(player2view, 0, context:GetHeight()/2, context:GetWidth(), context:GetHeight()/2)

 

Edit: I'll also add I've tried setting one of the cameras to Hidden, no effect change in result.

Edit2: I've also tried creating a new texture pragmatically and rendering that, same result.

[Admin]

It might be that the culling algorithm is blocking re-render. Do you have a simple test I can run?

[thehankinator]

See following post for script.

[thehankinator]

I had a chance to come up with a minimal script that removes the need for you to download the whole project. This has only one render target but has the same symptoms. You can press T to toggle between the render to texture and a straight render to the screen.

 

Main.lua

--Initialize Steamworks (optional)
Steamworks:Initialize()
--Set the application title
title="MyGame"
--Create a window
local windowstyle = window.Titlebar
if System:GetProperty("fullscreen")=="1" then windowstyle=windowstyle+window.FullScreen end
window=Window:Create(title,0,0,System:GetProperty("screenwidth","1024"),System:GetProperty("screenheight","768"),windowstyle)
window:HideMouse()
--Create the graphics context
context=Context:Create(window,0)
if context==nil then return end
--Create a world
world=World:Create()
local render_target = Texture:Create(512, 512)

local dir_light = DirectionalLight:Create()
dir_light:SetPosition(0,4,0)

local model = Model:Box()
model:SetColor(0.0,1.0,0.0)
model:SetPosition(0,0,0)

local camera = Camera:Create()
camera:SetPosition(-1,0,-1)
camera:SetRotation(0,45,0)
camera:SetRenderTarget(render_target)

local rot = 0;
local use_render_target = true

while window:KeyDown(Key.Escape)==false do

 --If window has been closed, end the program
 if window:Closed() then break end

 --Update the app timing
 Time:Update()

 context:SetColor(0,0,0)
 context:Clear()

 model:SetRotation(rot, 0, 0)
 rot = rot + Time:GetSpeed()

 if window:KeyHit(Key.T) then
   use_render_target = not use_render_target

   if use_render_target then
     camera:SetRenderTarget(render_target)
   else
     camera:SetRenderTarget(nil)
   end
 end

 --Update the world
 world:Update()

 --Render the world
 world:Render()

 if use_render_target then
   context:SetColor(1,1,1)
   context:DrawImage(render_target, 0, 0, 1024, 768)
 end

 context:SetBlendMode(Blend.Alpha)
 context:DrawText("Press T to enable/disable render target", 300, 2)

 --Refresh the screen
 context:Sync(true)
end

 

Edit: Why does the CODE tag always murder code formatting?

[thehankinator]

Anyone have an idea what I am doing wrong? Better yet, anyone have a working example using render targets?

[Josh]

I'm pretty sure what's happening is because the texture isn't bound during a world render, the camera assumes it has been culled and is skipping rendering.

 

I need to think about how best to handle this.

 

You could also just use a buffer, which is undocumented / unofficial. Basically like this:

buffer = Buffer:Create()

--Loop:
buffer:Enable()
world:Render()
context:Enable()
tex = buffer:GetColorTexture()
context:DrawImage(tex)

[Josh]

Here's an example for render targets:

--Create a window
window = Window:Create()
context = Context:Create(window)
world = World:Create()

camera = Camera:Create()
camera:SetRotation(35,0,0)
camera:Move(0,0,-6)

camera2 = Camera:Create()
camera2:Move(0,0,-4)
camera2:SetClearColor(1,0,0)
pivot = Pivot:Create()
camera2:SetParent(pivot)

local tex = Texture:Create(512,512)
local mtl = Material:Create()
mtl:SetShader("Shaders/Model/Diffuse.shader")
mtl:SetTexture(tex)
camera2:SetRenderTarget(tex)

local light = DirectionalLight:Create() 
light:SetRotation(35,35,0) 

local model = NULL 

model = Model:Box() 
model:SetPosition(-2,0,0) 
model:SetMaterial(mtl)

model = Model:Cylinder() 
model:SetColor(0.0,1.0,0.0) 
model:SetPosition(0,0,0) 

model = Model:Cone() 
model:SetColor(0.0,0.0,1.0) 
model:SetPosition(2,0,0) 

while true do

   pivot:Turn(0,0.5,0)

   if window:Closed() or window:KeyHit(Key.Escape) then return false end

   Time:Update()
   world:Update()
   world:Render()
   context:Sync()
end

[thehankinator]

Thanks for your help, using your example I can make a workaround until it's fixed. Buffer class looks much more simple, will it be going away? Will it ever become supported/documented?

[macklebee]

Buffer class looks much more simple, will it be going away? Will it ever become supported/documented?

I doubt it will go away since the post effect shaders wouldn't work without it. At this point, I don't understand why its not documented.

[Josh]

 

I doubt it will go away since the post effect shaders wouldn't work without it. At this point, I don't understand why its not documented.

I think it's time. There's a very specific case where this is useful.