scene_graph.py

# coding=utf-8
"""
Daniel Calderon, CC3501, 2019-2
A simple scene graph class and functionality
"""

from OpenGL.GL import *
import OpenGL.GL.shaders
import numpy as np

import transformations as tr
import easy_shaders as es


# A simple class to handle a scene graph
# Each node represents a group of objects
# Each leaf represents a basic figure (GPUShape)
# To identify each node properly, it MUST have a unique name
class SceneGraphNode:
    def __init__(self, name):
        self.name = name
        self.transform = tr.identity()
        self.childs = []

    
def findNode(node, name):

    # The name was not found in this path
    if isinstance(node, es.GPUShape):
        return None

    # This is the requested node
    if node.name == name:
        return node
    
    # All childs are checked for the requested name
    for child in node.childs:
        foundNode = findNode(child, name)
        if foundNode != None:
            return foundNode

    # No child of this node had the requested name
    return None


def findTransform(node, name, parentTransform=tr.identity()):

    # The name was not found in this path
    if isinstance(node, es.GPUShape):
        return None

    newTransform = np.matmul(parentTransform, node.transform)

    # This is the requested node
    if node.name == name:
        return newTransform
    
    # All childs are checked for the requested name
    for child in node.childs:
        foundTransform = findTransform(child, name, newTransform)
        if isinstance(foundTransform, (np.ndarray, np.generic) ):
            return foundTransform

    # No child of this node had the requested name
    return None


def findPosition(node, name, parentTransform=tr.identity()):
    foundTransform = findTransform(node, name, parentTransform)

    if isinstance(foundTransform, (np.ndarray, np.generic) ):
        zero = np.array([[0,0,0,1]], dtype=np.float32).T
        foundPosition = np.matmul(foundTransform, zero)
        return foundPosition

    return None


def drawSceneGraphNode(node, pipeline, transformName, parentTransform=tr.identity()):
    assert(isinstance(node, SceneGraphNode))

    # Composing the transformations through this path
    newTransform = np.matmul(parentTransform, node.transform)

    # If the child node is a leaf, it should be a GPUShape.
    # Hence, it can be drawn with drawShape
    if len(node.childs) == 1 and isinstance(node.childs[0], es.GPUShape):
        leaf = node.childs[0]
        glUniformMatrix4fv(glGetUniformLocation(pipeline.shaderProgram, transformName), 1, GL_TRUE, newTransform)
        pipeline.drawShape(leaf)

    # If the child node is not a leaf, it MUST be a SceneGraphNode,
    # so this draw function is called recursively
    else:
        for child in node.childs:
            drawSceneGraphNode(child, pipeline, transformName, newTransform)