Architecture

Viewline is a modern GPU-accelerated media viewer for animation, VFX, and OpenUSD workflows. It provides high-performance playback of video files, image sequences, and OpenUSD scenes through a unified OpenGL-based viewer.

Supported formats:

Video

MP4

MOV

AVI

Image Sequences

PNG

JPEG

EXR

3D Scene

USD

USDA

USDC

USDZ

Color Management

Viewline integrates OpenColorIO (OCIO) for consistent color management across all supported media types.

Features

OpenColorIO integration

ACES workflow architecture

Input color space selection

Display transform selection

Recommended Configuration

ACES 1.3 OCIO Config

System Architecture


                        Media Source

             (Video / Image Sequence / OpenUSD)
                              │
                              ▼
                        Media Reader
                              │
                ┌─────────────┴─────────────┐
                │                           │
                ▼                           ▼
        Video / Image Pipeline       OpenUSD Pipeline
                │                           │
                ▼                           ▼
            GPU Upload                Hydra Renderer
                │                           │
                ▼                           ▼
            GLTexture                 Render Delegate
                │                           │
                ▼                           ▼
            GLShader                     GLScreen
                │                           │
                └─────────────┬─────────────┘
                              ▼
                          GLScreen
                              │
                              ▼
                        QOpenGLWidget
                              │
                              ▼
               Display Output / Interactive 3D View

Rendering Architecture

Viewline uses a fully GPU-based rendering architecture where each rendering component has a dedicated responsibility.

Core Components

QOpenGLWidget

Creates the OpenGL context

Handles resize events

Displays the rendered output

Processes user interaction

GLScreen

Responsible for:

Render pass management

Frame presentation

Viewport updates

GPU resource coordination

GLTexture

Responsible for:

GPU texture allocation

Texture uploads

Texture updates

Texture lifecycle management

GLShader

Responsible for:

Shader compilation

Color processing

OpenColorIO transforms

GPU rendering

Viewer Settings

Video / Image

Display Settings

Exposure

Gamma

Brightness

Contrast

Saturation

Hue

Gain

Offset

Overlay

Style Settings

Sepia

Negative

Posterize

Gradient

Cartoon

Filter Settings

Sharpen

Blur

Motion Blur

Noise

Denoiser

OpenUSD Viewer

Display Settings

Shading Mode

Shaded Smooth

Shaded Flat

Wireframe

Wireframe on Surface

Points

Geom Only

Geom Smooth

Geom Flat

Complexity

Low

Medium

High

Very High

Display Purposes

Guide

Proxy

Render

Enable Scene Materials

Camera

Default Camera

Stage Cameras

Rendering Backends

Media Type	Reader	GPU Backend
Video	PyAV	Hardware Decode → OpenGL
Image Sequence	OpenImageIO	OpenGL Texture Rendering
OpenUSD	OpenUSD	Hydra Rendering

Python Requirements

Python-3.10.10 or +

Dependencies

Library Purpose

PySide6 UI framework

PyOpenGL OpenGL rendering

NumPy Image buffer processing

PyAV Video decoding

OpenImageIO Image sequence reading

OpenColorIO Color management

OpenUSD 3D Objects

Required Libraries


    requests: 2.32.2

        certifi: 2024.2.2 or +
        idna: 3.7 or +
        urllib3: 2.2.1 or +
        charset-normalizer: 3.3.2 or +

    PySide6: 6.9.0 or +

        shiboken6: 6.9.0 or +
        PySide6-Essentials: 6.9.0 or +
        PySide6-Addons: 6.9.0 or +

    pyqtdarktheme: 2.1.0 or +

        darkdetect: 0.7.1 or +

    OpenImageIO: 3.0.4.0 or +

    PyOpenGL: 3.1.9 or +

    opencolorio: 2.5.0 or +

    av: 17.0.0 or +

    OpenUSD: 26.05

    numpy: 1.26.4 or +

Recommended OCIO Config ACES 1.3

Official repository:

https://github.com/AcademySoftwareFoundation/OpenColorIO-Config-ACES

Open EXR Support

The player currently supports:

Single-layer EXR

Multi-layer EXR

RGB layer extraction

Basic AOV switching

The EXR reader automatically searches for valid RGB layers.

Example supported channel patterns:

    R G B
    beauty.R beauty.G beauty.B
    rgba.R rgba.G rgba.B
    Ci.R Ci.G Ci.B

Current Limitations

This project is currently an early playback framework.

Known limitations:

No threaded decoding
Image decoding may load many frames into memory
EXR playback currently converts float images into uint8 previews
No HDR display pipeline yet

Design Notes

Fully GPU-based rendering pipeline.
Unified viewer for video, image sequences, and OpenUSD.
Modular rendering architecture.
OpenGL shaders used throughout the rendering pipeline.
Hydra-based rendering for OpenUSD scenes.
OpenColorIO integration for color-managed workflows.
No legacy glDrawPixels() rendering.
Extensible architecture for future rendering backends.