box2d_sys 0.2.1

Bindings for Box2D v3.0
Documentation 
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// SPDX-FileCopyrightText: 2024 Erin Catto
// SPDX-License-Identifier: MIT

#version 330

uniform mat4 projectionMatrix;
uniform float pixelScale;

layout(location=0) in vec2 v_localPosition;
layout(location=1) in vec4 v_instanceTransform;
layout(location=2) in float v_instanceRadius;
layout(location=3) in float v_instanceLength;
layout(location=4) in vec4 v_instanceColor;

out vec2 f_position;
out vec4 f_color;
out float f_length;
out float f_thickness;

void main()
{
    f_position = v_localPosition;
    f_color = v_instanceColor;
    
    float radius = v_instanceRadius;
    float length = v_instanceLength;
    
    // scale quad large enough to hold capsule
    float scale = radius + 0.5 * length;
    
    // quad range of [-1, 1] implies normalize radius and length
    f_length = length / scale;
    
    // resolution.y = pixelScale * scale
    f_thickness = 3.0f / (pixelScale * scale);
    
    float x = v_instanceTransform.x;
    float y = v_instanceTransform.y;
    float c = v_instanceTransform.z;
    float s = v_instanceTransform.w;
    vec2 p = vec2(scale * v_localPosition.x, scale * v_localPosition.y);
    p = vec2((c * p.x - s * p.y) + x, (s * p.x + c * p.y) + y);
    gl_Position = projectionMatrix * vec4(p, 0.0, 1.0);
}