maszyna/docs/opengl46-renderer.md

OpenGL 4.6 renderer

The default renderer (gfxrenderer default, the modern backend, rendering/opengl46/) runs on an OpenGL 4.6 core profile context. There is no fallback to an older version, and the OpenGL 2.1 (legacy) renderer and the OpenGL ES / ANGLE path no longer exist.

For how the lights are handled, see clustered-lighting.md.

Requirements

• A graphics card and driver that provide OpenGL 4.6 (core profile). What the driver offers is written to the log at start: Renderer:, Vendor: and GL version:.
• A CPU with AVX2, as before.
• Windows and Linux. macOS provides OpenGL only up to 4.1, so the renderer does not run there.
• The experimental Better Renderer (gfxrenderer experimental) is a separate renderer and is not affected.

On Linux, glxinfo -B should report an OpenGL core profile version string of 4.6 or newer.

If the simulator does not start

When the context cannot be created, the log (log.txt) contains a line like

Bad init: failed to create OpenGL 4.6 core profile context (<GLFW error>); the graphics card/driver provides: OpenGL X.Y ..., <renderer> (<vendor>)

On Windows the same text is shown in a message box. Updating the graphics driver is the usual fix; a card which does not support OpenGL 4.6 cannot run this renderer. The process ends with a non-zero exit code.

eu07.ini

Removed options

Old eu07.ini files still load. These entries are read and ignored, with a line in the log:

Entry	What happens now
gfxrenderer legacy, simple or any other value except default, full and experimental	the default renderer is used (eu07.ini: gfxrenderer "X" is no longer supported, using "default")
usevbo	ignored (eu07.ini: "usevbo" is no longer supported and was ignored)
gfx.usegles	ignored, same message
gfx.angleplatform	ignored, same message

gfxrenderer full is still taken for default.

New options

Entry	Default	Meaning
gfx.lights.clustered yes/no	yes	yes: every lit vehicle headlight within 1 km lights the surroundings (see below). no: the shading goes through the first dynamiclights headlights only, as the old renderer did; useful to compare images or to work around a problem
gfx.lights.clusterheatmap yes/no	no	debug view: the number of lights in each cluster, drawn over the image

Changed option

dynamiclights (0..7) used to limit the number of headlight sets that light the surroundings. It is still read, but it only takes effect with gfx.lights.clustered no.

What looks different from the previous renderer

• No limit of 7 lit headlights. All lit headlights within 1 km take part in the lighting (each lit end of a vehicle counts separately), up to 255 in the buffer and 64 reaching any one part of the view. Beyond these capacities the farthest and dimmest lights are dropped, and the statistics show how many.
• Outside the beam texture a headlight adds nothing. Before, the edge of the texture was stretched beyond the beam, which could leave a faint glow around vehicles. This also applies with gfx.lights.clustered no.
• Reflections (environment map) are lit with the sun as seen from the reflection itself, and vehicle headlights no longer light the scene in them.
• Motion blur and SSAO read the real depth of the scene. Before, the depth texture was read in a way the specification leaves undefined, and the result depended on the driver.
• Lines are 1 pixel wide, as they always were on this kind of context. The widths the code asked for (catenary wires, map tracks) never took effect.

The editor (F11, orthographic view), the reflection pass and the model previews do not use clusters. The editor goes through the first dynamiclights headlights, the reflections through the sun only.

Statistics and debugging

• Shift+F12, Gfx Renderer: the lights: row gives the number of lit headlight sets, how many did not fit, and clustered or first N. With clusters on, clusters: (rebuilding of the grid, which happens when the projection or the draw range change) and cull: (assigning lights to clusters, every frame) show the GPU time, and cluster lists: the size of the lists and the number of dropped (cluster, light) pairs (overflow, with its peak). A non-zero overflow means some cluster held more than 64 lights.
• Light clusters window (in debug mode, menu Windows, item Headlight config opens the renderer debug windows): the switch for clustered lights, the heat map, the grid state and the same counters.
• gfx.gldebug yes turns on the OpenGL debug output (KHR_debug); messages go to the log.

Building

-DWITH_OPENGL_MODERN=ON (default) builds this renderer; WITH_OPENGL_LEGACY and the GLES / ANGLE options are gone. Linux builds still use -DWITH_BETTER_RENDERER=OFF.

All shaders in shaders/ can be checked without a graphics card against GLSL 4.60, compute stage included:

ci_shadervalidator/build.sh
cd ci_shadervalidator && ./validateshaders

It needs g++ with C++20, glslangValidator (Debian/Ubuntu: glslang-tools) and the ref/glm submodule. The same check runs in CI for changes to shaders and the gl/ wrappers.