Using the Qt Quick Scene Graph API
summary
Explains how using the Qt Quick Scene Graph API and a few lines of C++—replacing many QML rectangles with one QQuickItem that implements updatePaintNode and a custom QSGGeometry/QSGMaterial—moves per-dot position and opacity math into the vertex shader, collapsing thousands of draw updates into a single GPU-driven batch. A QR-code demo goes from ~100% CPU and stuttering to ~12% CPU while keeping 60 FPS; warns that transparent nodes force rebatching and shows how to avoid that.
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chapters (12)
- 0:00Introduction and background
- 1:55Origin of the scene graph
- 8:14Scene Graph node basics
- 11:26Implementing updatePaintNode
- 16:30Scene Graph threading model
- 19:20Performance bottleneck example
- 26:24Moving logic from QML to C++
- 33:22Batching and rendering issues
- 35:49Custom geometry nodes
- 41:10GPU animation with shaders
- 47:18Performance gains with GPU
- 49:02Resources and conclusion
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