coordinate-system-convention.txt

Model -> World -> View -> Projection -> NDC -> Screen -> shs::Canvas



Model space 3D coordinate system:
    origin is (0,0,0) and center of all vertices of individual model
    x is to the right
    y is to the up
    z is to the forward


World space 3D coordinate system
    origin is (0,0,0) and center of all models
    x is to the right
    y is to the up
    z is to the forward


View space 3D coordinate system
    origin is (0,0,0) and viewer is at origin, all models are on this coordinate system
    x is to the right
    y is to the up
    z is to the forward


Projection space coordinate system
    used for simulating camera perspective
    x is to the right
    y is to the up
    z is to the forward
    w is used for normalization


Clip space aka NDC(Normalized Device Coordinates) space aka homogeneous coordinate space
    axis are mapped to range of [-1.0, 1.0], scaled by z_near and z_far
    x is to the right
    y is to the up
    z is to the forward

    glm::vec3 point_in_NDC = glm::vec3(point_in_CLIP_SPACE) / point_in_CLIP_SPACE.w;


Screen space 2D coordinate system
    maps x in NDC[-1, 1] -> [0, SCREEN_WIDTH ]
    maps y in NDC[-1, 1] -> [0, SCREEN_HEIGHT]
    origin (0,0) is at top-left corner
    x is from left to the right
    y is from top to the bottom

    Rasterizatin happen in this space


shs::Canvas 2D coordinate system:
    origin (0,0) is at left-bottom corner
    x is left to right
    y is bottom to up



Converting from Screen space to the shs::Canvas space
    x_at_canvas = x_at_screen_space
    y_at_canvas = SCREEN_HEIGHT - y_at_screen