Implementation:Google deepmind Mujoco mjr readPixels

Knowledge Sources	MuJoCo MuJoCo API Reference
Domains	Rendering, Computer_Vision, OpenGL
Last Updated	2026-02-15 06:00 GMT

Overview

Concrete tool for reading rendered pixels from an OpenGL framebuffer provided by the MuJoCo rendering API.

Description

The mjr_readPixels function reads RGB color and/or depth data from the currently active OpenGL framebuffer into CPU memory buffers. When reading from a multisampled offscreen FBO, it performs a resolve-blit first. Companion functions mjr_setBuffer and mjr_maxViewport control which framebuffer is active and query its dimensions.

Usage

Call after mjr_render to capture the rendered frame. Set mjFB_OFFSCREEN buffer first for headless rendering. Pass NULL for rgb or depth to skip that readback.

Code Reference

Source Location

• Repository: mujoco
• File: src/render/render_gl2.c
• Lines (mjr_readPixels): 139-148
• Lines (mjr_setBuffer): 33-77
• Lines (mjr_maxViewport): 635-648

Signature

void mjr_readPixels(unsigned char* rgb, float* depth,
                    mjrRect viewport, const mjrContext* con);
void mjr_setBuffer(int framebuffer, mjrContext* con);
mjrRect mjr_maxViewport(const mjrContext* con);

Import

#include <mujoco/mujoco.h>

I/O Contract

Inputs

Name	Type	Required	Description
rgb	unsigned char*	No	Output RGB buffer (3 bytes/pixel, NULL to skip)
depth	float*	No	Output depth buffer (1 float/pixel, NULL to skip)
viewport	mjrRect	Yes	Rectangle defining which pixels to read
con	const mjrContext*	Yes	Active rendering context
framebuffer	int	Yes	mjFB_WINDOW or mjFB_OFFSCREEN (for mjr_setBuffer)

Outputs

Name	Type	Description
rgb (modified)	unsigned char*	Raw RGB pixel data (3 * width * height bytes)
depth (modified)	float*	Depth values in [0, 1] (width * height floats)
return (mjr_maxViewport)	mjrRect	Maximum viewport dimensions for active buffer

Usage Examples

#include <mujoco/mujoco.h>

// Switch to offscreen buffer
mjr_setBuffer(mjFB_OFFSCREEN, &con);

// Get maximum viewport
mjrRect viewport = mjr_maxViewport(&con);

// Render to offscreen buffer
mjv_updateScene(m, d, &opt, NULL, &cam, mjCAT_ALL, &scn);
mjr_render(viewport, &scn, &con);

// Read pixels
int W = viewport.width;
int H = viewport.height;
unsigned char* rgb = (unsigned char*)malloc(3 * W * H);
float* depth = (float*)malloc(sizeof(float) * W * H);
mjr_readPixels(rgb, depth, viewport, &con);

// Process or save pixels...
free(rgb);
free(depth);

Related Pages

Implements Principle

• Principle:Google_deepmind_Mujoco_Offscreen_Rendering

Requires Environment

• Environment:Google_deepmind_Mujoco_C_Build_Environment