hop-engine

a work-in-progress graphics engine focused on complex, non-destructive multi-step realtime art and videogame rendering worflows. intended to be a powerful but simple-to-use editing and rendering toolkit.

Features (old)

• render graph - a system for specifying a series of camera (scene rendering) or post-process (fullscreen-quad rendering) steps where the output attachments of previous steps can be chained as inputs to future steps (e.g. feeding the normal and depth buffers from a camera step into an SSAO post-process step). allows for complex multi-step post-processing, modifiable and debuggable at runtime! (see inc/render_graph.h)

• normal mapping - normal maps are sampled and the results are transformed to world-space for lighting calculations (see res_engine/shaders/pbr_util.glsl)

• deferred rendering - a two-pass deferred rendering approach is supported, taking 5 attachments as inputs (albedo, normal, roughness/metallicness/emission, specular, depth) and sampling multiple lights using PBR shading. this is used for all objects in the museum scene (see res_engine/shaders/deferred.frag and res_engine/shaders/deferred_post.frag)

• PBR shading - simple PBR shading is implemented using roughness and metallic parameters, in addition to surface albedo, normal, and specular colours. this shading is available both in deferred and forward rendering modes (see res_engine/shaders/pbr_util.glsl)

• SSAO - screen space ambient occlusion is a great use of multi-step post-processing, and makes scenes feel much more realistic to look at (see res_engine/shaders/effects.glsl and res_engine/shaders/ssao.frag)

• blur effects - functionality for sampling generic convolution kernels is provided, as well as example implementations for 5x5 and 9x9 Gaussian blur kernels. this is used to smooth the SSAO result (see res_engine/shaders/effects.glsl and res_engine/shaders/blur.frag)

• colour grading and LUT post processing - a colour grading and LUT post-processing effect is included to demonstrate colour-based post-processing. makes the museum look lovely and sepia-toned. or you can ruin it by playing with the sliders in ImGui i guess... (see res_engine/shaders/colour_correct.frag)

• text rendering - a bitmap text rendering object allows runtime-editable text rendering, providing in-game instructions for the museum demo! (see res_engine/shaders/text.frag and inc/text_block.h)

• on-GPU frame duration information via query pool - using the Vulkan QueryPool primitive, detailed statistics about how long the frame took to render on the GPU are recorded, including breakdowns of time spent in each render pass (see src/graphics_environment.cpp)

• render-to-texture can be bound and shown on an object in the scene

• museum and bunnygirl demo scenes - two demo scenes are provided, the first being a much more comprehensive demonstration of graphics techniques. the other is still here for fun though! (see res/museum, src/museum_scene.cpp, and src/asha_scene.cpp)

• scene heirarchy & nested transform tree - allows for all the transform behaviours you'd expect. see the orrery in the center of the museum scene for a great demo! (see inc/scene.h and inc/transform.h)

• resource packaging - instead of having a hundred individual files hanging around, the engine supports loading (and storing) '.hop' package files, from which resources can be loaded by referencing their file path prefixed by res://. supports ZIP compression, resource aliasing, and overwriting on load, allowing for easy modding of existing executables by simply loading an extra resource package! (see src/package.cpp, src/package-builder/package-builder.cpp res, and res_engine)

• scene, material, and render graph deserialisation from text representations - a minimal library for decoding abstract syntax trees and extracting statements is provided, which forms the basis for various deserialisers (more to come in the future) (see src/deserialise.cpp)

• automatic reference counting - custom smart-pointer-like reference counted types are provided which are intended to wrap nearly all engine types. comes in strong and weak varieties, with constructors and assignment operators for minimal annoyance during usage! (see inc/counted_ref.h)

• keyboard and controller input - a simple framework for grabbing keyboard and mouse input (both in terms of current state or 'pressed-since-last-checked'), as well as gamepad input. provides functions for treating pairs of keyboard keys as virtual gamepad axes. used for all input functionality by the demo scenes (see inc/input.h)

• detailed ImGui debug controls - extensive ImGui interactivity allows you to see the states of most engine types, as well as modify most of their parameters. missing some support currently (see src/imgui_functions.cpp)

• object picking via ray-OBB intersection testing - exactly what it says. would benefit from being able to see the bounding box of the object you have selected! (see inc/math_helpers.h)

• material abstraction via shader reflection - uniform variables and textures can be easily assigned by name, updating of descriptor sets is managed automatically, and uniform type size checking is performed automatically (see inc/material.h)

• detailed console debug output - variable degrees of verbosity; passthrough of the Vulkan validation layers (if enabled); outputs both to the console (with colours!!) and a log file. just makes life easier (see inc/debug.h)

Credits

the beautiful skybox is a slightly modified (adding the checkerboard floor) version of the NASA SVS Deep Star Maps 2020. credit for this:

NASA/Goddard Space Flight Center Scientific Visualization Studio. Gaia DR2: ESA/Gaia/DPAC. Constellation figures based on those developed for the IAU by Alan MacRobert of Sky and Telescope magazine (Roger Sinnott and Rick Fienberg).

libraries used:

• Vulkan
• GLFW
• glm
• ImGui
• SPIRV-reflect
• shaderc
• STB Image
• base64

all other assets (models, materials, textures, shaders, font, and demo scenes) are made by me. and the code obviously.

particular thanks to LearnOpenGL, the Vulkan Tutorial, and David White for the guidance to develop this.

additional thanks to Lucy and Louise for keeping me alive and sane. <3