How to Render Pixelated Lines in OpenGL While Scaling to Different Resolutions?

OpenGL Scale Single Pixel Line

In your query, you express the desire to create a game that maintains a 320x240 internal resolution while scaling its output to multiples of this resolution on screen. Your current approach, however, results in 1px lines being rendered in a 3px world when scaling up to 960x720.

The issue stems from the assumption that you can render to a "320x240 glOrtho canvas." In reality, there is only a single active window resolution: 960x720. Your code lediglich scales the coordinates of the primitives that you render.

To resolve this, you need to abandon the notion of a separate "320x240 glOrtho canvas" and instead focus on the window's actual resolution. This entails rendering to an image that is genuinely 320x240 before drawing it to the window's actual resolution.

The specific steps for this process involve creating a texture of 320x240, attaching it to a framebuffer object, and binding the FBO for rendering. The viewport should be set to the image's size. After unbinding the FBO, you can draw the texture to the window with the viewport set to the window's resolution.

This method allows you to retain pixelated line rendering and accommodate various output resolutions while preserving the game's internal 320x240 resolution.

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