Update 0.7 - Changelog

A new update adds more simulation options, improves shadow rendering, allows objects to pass through wormholes, and much more.

The update is available to all Patrons. You can download it in the patron-only channel on Discord.

Shadows for the real-time renderer

The rendering of shadows has been completely rewritten, as described in the previous development update. It now uses shadowmaps and should generally produce much more accurate results than the previous system.

There are several parameters in the render settings that tweak the behavior and quality of shadows, namely:

• Shadowmap resolution determines the quality of shadows. Higher values improve the shadows but require more VRAM and slow down the rendering.

• Adaptive makes the shadow adjust to the current camera view. You can disable it if you see shadows changing noticeably when moving the camera.

• Max cast distance is used so that distant objects do not reduce the shadow quality.

While the previous system created semi-transparent spherical shadows, the new shadows are always solid, reflect the real shapes of objects and can be cast by individual particles.

Colored shadows

Raymarched shadows also received a small improvement. The absorption coefficient now takes into account the color of the gas, which makes gas particles cast colored shadows. This allows for a more realistic atmosphere rendering, with a blue color when illuminated directly by the Sun and a reddish hue near the terminator, similar to the color of a sunset on Earth.

Colored shadows are always enabled and do not require any special parameters.

Viscosity & Friction

As showcased in the previous development update, it's now possible to realistically simulate the viscosity of the material. When enabled, it adds a force that acts against the deformation rate of particles, slowing down their movement. The viscosity only "activates" when particles move, the force is zero when the particles are at rest or moving with constant velocity. Unlike cohesion, viscosity cannot hold the shape of objects, it can only slow down the deformation.

The force due to viscosity depends on the material parameter 'dynamic viscosity' which can be modified in the material settings.

Shaped objects in a gravitational field, made of material with a high value of dynamic viscosity.

Another simulation option added in the update is friction, which is currently only applied between particles and rigid (non-deformable) objects. Similarly to viscosity, it adds additional force when particles move along the surface of rigid objects. The magnitude of the friction is determined by the material parameter called 'dry friction'.

Normal maps

The surface of planets can now be enhanced using normal maps, showing craters, mountains, valleys and other topographic features. Normal maps can be set in the texturing parameters, similar to the diffuse or specular textures. If you want to use a height map (or displacement map) instead, you need to convert it to a normal map first - this can be done easily using GIMP or similar software.

Normal maps have been added to both the real-time renderer and the raymarcher and should give consistent results.

Moon with (right) and without (left) normal maps.

White holes and Wormholes

The update adds an option to change a black hole into a white hole. White holes are time-reversed black holes. While things can only enter a black hole and nothing can leave it, the white hole is the opposite - nothing can enter and things can only leave it. Unlike black holes, white holes are purely theoretical objects and have not been observed in reality.

As SpaceSim implements Newtonian gravity, both the black holes and white holes are highly simplified in the simulation. Black holes can only absorb particles and white holes can only repel them.

Furthermore, it's possible to connect a black hole to a white hole to form a wormhole. A wormhole acts as a portal in space and everything that falls into it is ejected from the other end, with the same velocity it had when absorbed.

Black hole formation

Black holes can also be created during the simulation. Whenever an object is dense enough that their radius falls below its Schwarzschild radius, a "seed" black hole is added to the center of the object, starts absorbing particles and grows until the whole object is absorbed. There is also a new preset 'Collapse to Singularity' that shows the formation of black holes from a cloud of dense matter.

The formation of black holes can be enabled in the simulation settings, under 'Events' tab.

Heat conduction

Another simulation feature added in the update is heat conduction (or diffusion), allowing the heat to flow from hot particles to cold particles.

With default settings, the effects of heat conduction is negligible. To make the effect noticeable, it's necessary to either significantly increase the time step, or set a much higher heat conductivity in the material settings.

Heat conduction can be enabled or disabled in the simulation settings.

Reworked simulation history

The simulation history has been changed significantly, improving the handling of simulation state files. You no longer decide whether to save the history when saving the simulation, instead the history is always saved when the 'save to disk' option is enabled. In case the app closes due to PC restart or a crash, you can still retrieve the entire recorded history. It is also possible to import/export the history manually.

The available options for history state files are:

• Never - the simulation is only stored in memory, no files are created on disk.

• Last simulation - the app saves files of the most recent simulation, allowing to retrieve the simulation in case the app closes unexpectedly.

• Every simulation - the app saves all started simulations and allows to select which simulation to show in the simulation tab. This is useful for comparing simulations with different settings.

Furthermore, you can now decide what happens when the simulation history runs out of allocated memory. You can either remove the first state in the history (which is how it worked in the previous version), or you can remove intermediate files, keeping the full span of the simulation at a cost of losing some accuracy. This is the new default.

Other simulation improvements

• Particle-removing boundary is a new type of boundary conditions that removes all particles that fly outside of the simulation domain. It can be used as an optimization, removing distant isolated particles that don't affect the rest of the simulation.

• The core of a planet can be made rigid, replacing particles with a non-deformable sphere. This allows you to increase the resolution near the surface of the planet, create a more detailed simulation of an atmosphere, etc.

• The atmosphere layer of planets can include clouds, clumps of particles made of a different material, which add some variation to the planetary surface. This is somewhat similar to the 'sunspots' of stars added a few versions ago.

• Inspired by a Kurzgesagt video, the update adds a new material - strange matter. Particles made of strange matter convert any other material into more strange matter when they collide. A preset 'strange planet' shows the strangelet conversion in action.

• Black holes have an option to set an arbitrary radius. By default, the radius is equal to the Schwarzschild radius for a given mass.

• You can now save custom materials, similarly to saving custom objects. Custom materials persist between simulations and are stored as .mtl file in %localappdata%/spacesim/materials.

Graphics improvements

• The renderer now uses a logarithmic depth buffer, which fixes a number of artifacts, especially when rendering objects of significantly different sizes.

• The emission magnitude of solid and gas particles is now set separately, using material parameters 'surface emission' and 'emission coefficient', respectively. As a consequence, the emission of gas particles is now more consistent and independent of the total number of particles.

• Grid lines now automatically adjust to the camera position and zoom, show distance labels along the x and y axes, and can be optionally enabled during the simulation.

• The rendering of object trajectories, orbits and trails has been reworked. It improves antialiasing, makes the trajectories independent of the bloom settings, and should look consistent between different GPUs and drivers.

• Trajectories and grid lines are also correctly sorted with gas particles. Previously they were always rendered on top of gas, regardless of the gas opacity.

  

• All overlay options (Roche limit, spin axes, etc.) are independent of postprocessing settings.

• Improved the normal interpolation when using the raymarcher, resulting in a generally smoother surface and making individual particles less visible.

• Added two new clip modes. Material mode shows only particles of the given material, and interior mode hides all particles inside objects, keeping only the surface particles. The interior mode is mainly used as a rendering optimization.

• The real-time renderer and raymarcher now share the light and shadow toggles.

UI

• The update completely reworked the way new objects are added into the simulation. Instead of placing them automatically at predefined positions, you can now place them manually by picking the desired position. The position of objects snaps to the grid when holding Ctrl.

• Similarly, objects can be placed at any position when using copy+paste (Ctrl+C - Ctrl+V).

• UI elements, such as color palette, current time and distance measure, can be optionally included in the rendered video.

• Improved the typesetting of physical quantities.

  

• Panels and the menu have been tweaked a bit. All panels now have a "burger" menu at the top.

• Preferences now show all the hotkeys available in the application. The hotkeys will be editable in future updates.

New content

There are a few simulation presets showcasing the new features:

• Collapse to Singularity shows the formation of black holes from the collapse of a dense gas cloud.

• Heat Conduction is a simple demonstration of the eponymous simulation feature.

• Strange Planet shows the effect of strange matter when a small asteroid made of strange matter collides with a planet and its ring.

• TYC 7037-89-1 utilizes the barycenter object added in the previous update to set up a complex hierarchical star system.

• Chthonian Planet is a simulation showing the formation of a hypothetical planet, by stripping the mantle of a gas giant due to extreme radiation pressure of the parent star.

New objects:

• Primordial black hole - a hypothetical type of a black hole, much smaller than the stellar-mass black holes or supermassive black holes.

• White hole - a time-reversed variant of a black hole.

• Elliptical galaxy - a spherically symmetric galaxy, smaller compared to the disk galaxy.

• Planetary nebula - uses the molecular cloud object with the 'blob' shape to create a colorful nebula.

That's it for now. Stay tuned for more development updates.