# Copyright (c) 2019, NVIDIA CORPORATION. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from abc import abstractmethod
import torch
[docs]class DifferentiableRenderer(torch.nn.Module):
r""" Base class for differentiable renderers. All major components
of the graphics processing pipeline have been instantiated as
abstract methods.
A differentiable renderer takes in vertex geometry, faces (usually
triangles), and optionally texture (and any other information
deemed relevant), and implements the following main steps.
* Lighting (ambient and optionally, directional lighting, i.e.,
diffuse/Lambertian reflection, and optionally specular reflection)
* (Vertex) Shading (Gouraud/Phong/etc.)
* Geometric transformation (usually, this is needed to view the
object to be rendered from a specific viewing angle, etc.)
(the geometric transformations are usually applied AFTER lighting,
as it is easier to perform lighting in the object frame, rather
than at the scene level)
* Projection (perspective/orthographic/weak-orthographic(affine))
from 3D (camera) coordinates to 2D (image) coordinates.
* Rasterization to convert the primitives (usually triangles) to
pixels, and determine texture (when available).
"""
@abstractmethod
def __init__(self):
super(DifferentiableRenderer, self).__init__()
@abstractmethod
def forward(self, vertices, faces, textures=None):
# Generally, this method will call the other
# (already implemented) methods.
# self.lighting()
# self.shading()
# self.transform_to_camera_frame()
# self.project_to_image()
# self.rasterize()
raise NotImplementedError
@abstractmethod
def lighting(self):
raise NotImplementedError
@abstractmethod
def shading(self):
raise NotImplementedError
@abstractmethod
def transform_to_camera_frame(self):
raise NotImplementedError
@abstractmethod
def project_to_image(self):
raise NotImplementedError
@abstractmethod
def rasterize(self):
raise NotImplementedError