vertex.py

# vertex.py

from enum import Enum

class VertexSpace(Enum):
    """
    Enumerates the coordinate space a vertex is currently in.
    This makes pipeline stages explicit and type-safe.
    """
    OBJECT = 0     # Object / model space
    CLIP   = 1     # Clip space (after vertex shader)
    NDC    = 2     # Normalized Device Coordinates
    SCREEN = 3     # Screen / framebuffer space


class Vertex:
    """
    Simple per-vertex container used throughout the rasterization engine.

    Notes
    -----
    • x, y, z represent position, whose meaning depends on `space`
    • w is the homogeneous clip-space component
    • attrs / varyings store per-vertex interpolated data
    """

    def __init__(self, x=1.0, y=1.0, z=1.0, r=0.0, g=0.0, b=0.0, w=1.0):
        # Position
        self.x = x
        self.y = y
        self.z = z

        # Color (optional / legacy)
        self.r = r
        self.g = g
        self.b = b

        # Homogeneous clip-space w
        self.w = w

        # Track current pipeline space
        self.space = VertexSpace.OBJECT

        # Generic per-vertex attributes (varyings)
        self.attrs = {}
        self.varyings = self.attrs


    def copy(self):
        """
        Create a deep copy of this vertex, including varyings.
        """
        v = Vertex(self.x, self.y, self.z, self.r, self.g, self.b, self.w)
        v.space = self.space
        v.attrs = dict(self.attrs)
        v.varyings = v.attrs
        return v

    def attach_varying(self, name, value):
        """
        Attach a varying value (normal, uv, pos_view, etc.) to this vertex.

        This is just a convenience wrapper around self.attrs[name] = value.
        """
        self.attrs[name] = value

    def get_varying(self, name, default=None):
        """
        Retrieve a varying value by name.

        This is equivalent to self.attrs.get(name, default).
        """
        return self.attrs.get(name, default)