Changing Minecraft's Viewport Render Size

[AutogolazzoJr]

Hello, I am making a coremod that renders the game in two separate viewports that are slightly different to be used for cross-eyed 3d viewing. Basically it looks like this:

I am currently using MCP reborn (MCP for 1.15.2) instead of forge right now due to ease of use, but I plan to make this a coremod later and I don't know where I can get better help for modding right now than this site.

Currently, I have achieved this by modifying 

net.minecraft.client.renderer.WorldRenderer.func_228426_a_(WorldRenderer.java:841)
[14:51:27] [Render thread/INFO]: [STDERR]: 	at net.minecraft.client.renderer.GameRenderer.renderWorld(GameRenderer.java:593)
[14:51:27] [Render thread/INFO]: [STDERR]: 	at net.minecraft.client.renderer.GameRenderer.updateCameraAndRender(GameRenderer.java:420)
[14:51:27] [Render thread/INFO]: [STDERR]: 	at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:909)
[14:51:27] [Render thread/INFO]: [STDERR]: 	at net.minecraft.client.Minecraft.run(Minecraft.java:544)
[14:51:27] [Render thread/INFO]: [STDERR]: 	at net.minecraft.client.main.Main.main(Main.java:177)

I then run most of the code inside of this method twice, excluding the code that clear the screen, but I run RenderSystem.viewport() each time to change the position and scaling of each image. However, using this method only scales the viewport, and it results in each image being squished and looking terrible. It looks like this:

How can I get minecraft to actually render the world at half the width instead of simply scaling down the image? Where do the world render methods actually look for the resolution to render at?

Any help would be appreciated. Thanks.

[AutogolazzoJr]

25 minutes ago, diesieben07 said:

Jarmodding is not supported on this forum.

Especially for something that does not even need to be a coremod.

This does not need to be a coremod? Can you elaborate on how this can be done?

[AutogolazzoJr]

Thanks. I'm still a bit lost. How does the game know what size to render the world at? Where are these variables located?