AgentSkillsCN

render-gl

运用OpenGL 4.1核心渲染模式。在修改视口、草图渲染器，或新增可视化元素时使用。

SKILL.md
--- frontmatter
name: render-gl
description: OpenGL 4.1 Core rendering patterns. Use when modifying viewport, sketch renderer, or adding visual elements.
invocable: true
author: OneCAD
license: MIT
metadata:
  category: rendering
  priority: medium

When to Use

  • •Adding new rendered elements
  • •Modifying Camera3D/Grid3D
  • •Shader development
  • •Debugging visual glitches

Architecture

  • •Camera: src/render/Camera3D.h/cpp
  • •Grid: src/render/Grid3D.h/cpp
  • •SketchRenderer: src/core/sketch/SketchRenderer.h/cpp (1903 LOC)
  • •BodyRenderer: src/render/BodyRenderer.h/cpp (727 LOC)
  • •Viewport: src/ui/viewport/Viewport.h/cpp (3146 LOC)

OpenGL 4.1 Core Profile

OneCAD uses OpenGL 4.1 Core (no fixed-function pipeline).

Critical Patterns

GL State Bind/Unbind Pairs

cpp
// ALWAYS unbind what you bind
glBindVertexArray(vao);
// ... draw calls ...
glBindVertexArray(0);

glBindBuffer(GL_ARRAY_BUFFER, vbo);
// ... operations ...
glBindBuffer(GL_ARRAY_BUFFER, 0);

program->bind();
// ... draw ...
program->release();

Shader Program Pattern

cpp
QOpenGLShaderProgram program;
program.addShaderFromSourceCode(QOpenGLShader::Vertex, vertexSrc);
program.addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentSrc);
program.link();

VAO/VBO Setup

cpp
GLuint vao, vbo;
glGenVertexArrays(1, &vao);
glGenBuffers(1, &vbo);

glBindVertexArray(vao);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, size, data, GL_STATIC_DRAW);

// Position attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, stride, (void*)0);
glEnableVertexAttribArray(0);

glBindVertexArray(0);

Camera3D

cpp
// Orbit/pan/zoom
camera.orbit(deltaX, deltaY);
camera.pan(deltaX, deltaY);
camera.zoom(delta);

// View/projection matrices
QMatrix4x4 view = camera.viewMatrix();
QMatrix4x4 proj = camera.projectionMatrix();

// Ortho ↔ Perspective (scale-preserving)
camera.setOrthographic(true);

Grid3D

  • •Fixed 10mm grid spacing
  • •Shader-based rendering
  • •Adapts to zoom level

SketchRenderer Preview Methods

cpp
void setPreviewLine(const Vec2d& start, const Vec2d& end);
void setPreviewCircle(const Vec2d& center, double radius);
void setPreviewArc(const Vec2d& center, double radius,
                   double startAngle, double endAngle);
void clearPreview();

void showSnapIndicator(const Vec2d& pos, SnapType type);
void setGhostConstraints(const std::vector<InferredConstraint>& ghosts);

Common Issues

  1. •State leaks: Always unbind resources
  2. •Missing makeCurrent(): Call before GL operations
  3. •Thread safety: GL context is single-threaded
  4. •Depth testing: Enable/disable appropriately
  5. •Blending for transparency: GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA