Plugins + Scripts [ForgeLab] Glass Forge

She is on the other side of it, and she knows exactly how much it is showing.

The pane has gone soft with heat. Not opaque. Worse than opaque. It keeps a shape, a shoulder, the dark of her hair, and takes away every detail that would settle the question. She has been standing there long enough for the water to find its way down the glass in the slow, wandering lines that water actually takes, and each one that runs opens a clear stripe behind it, and closes again.

Then she puts a hand flat against it and draws it down.

Where her palm went, the fog is gone. A window the width of her hand, and behind it, in focus, wet, unhurried: her. The rest of the glass stays exactly as fogged as it was. She does not wipe the whole pane. She never does. She gives you the strip she decided on, watches you through it, and lets the heat close it again while you are still looking.

And when it does close, when there is nothing to see again, you find out the glass was never the safe part of this.

It gives when you push. And then it gives all at once.

Now count how much of that VAM cannot do. It has no glass you can put a hand through. Nothing that fogs and stays fogged where you did not touch it. Nothing that reflects the actual room instead of a cubemap someone baked in 2019. And nothing, anywhere, that breaks.

There are glass props. They are pictures of glass.

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Not a trigger you fire. Not an animation you play. The pane has colliders, the impact has an impulse, and the impulse decides.

You will probably find this out before you read any of it, because a pane that gets knocked on load will break on load, and the Rebuild button is right underneath. That is on purpose. It tells you in the first two seconds what kind of object this is.

Cracked is a state, not a step on the way to broken

There are two thresholds, and the gap between them is the whole feature.

Hit it below the first one and nothing happens. Hit it between the two and the glass cracks and stays cracked: a real fracture pattern spreading from the point of contact, frosted along the break, still one solid pane you can lean on. Hit it above the second and it goes.

So you can knock. You can crack it and leave it cracked for the rest of the scene. You can crack it three times in three places and then break it. Both thresholds are sliders in impulse units, which means "how hard" is a number you tune rather than a mode you pick.

Or break it on purpose and then arrange the pieces



The shards are real rigid bodies. Count per face, burst speed, and whether they collide with each other are all yours.

Which makes this workflow possible, and it is the one people are going to keep:

1. Turn Freeze Settled Shards off
2. Hit SHATTER
3. Grab the pieces with your hands and put them where you want them: mid-air, on the floor, balanced against her
4. Press Freeze Shards Now

Everything stops exactly where you left it and stays there. You have just used a physics simulation as a modelling tool, and the result costs nothing to hold.

Left on its default, shards freeze themselves a few seconds after they settle, which is the same saving without the arranging.

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Condensation is a full-surface fog with an amount slider, and it picks up the glass's own tint so fogged blue glass stays blue.

Touch Wipe is the part that matters. Anything that touches the glass clears it, and it clears along the contact path, not in a stamp where the hand ended up. Drag a palm down and you get the streak a palm makes. Drag a finger and you get a line.

Which means you can write on it.

Then it fogs back over

Re-fog Time decides how long the clear stays. Set it short and a handprint is gone in a few seconds, which is the version that reads as a hot shower. Set it to zero and the clear is permanent: anything wiped stays wiped, which is the version you want when you are drawing something you would like to keep.

And a rectangle you can place, for when you want a window

Fog Wipe Zone is a separate, authored clear area: position, size, and edge softness. Use it for the strip at eye height that someone already wiped before your scene started. It is drivable from Timeline like everything else, so it can open as the scene runs.

And water runs down it
Wandering trails, not straight lines



The other half of a wet pane. Rain on a window, a shower running down the door. The drips wander, gather, and speed up as they collect, because water on glass does not fall in a straight line, and a straight line is the thing that instantly reads as fake.

Density, speed and size are three sliders. Set the speed to zero and they stop, which gives you glass that has been wet for a while rather than glass that is being rained on right now.

Each trail opens a clear channel through the condensation as it goes. Fog plus drips is the combination worth trying first: the fog is what hides her, and the drips are what keep taking little pieces of that away.

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The reflection is rendered from the mirrored position of whatever camera is looking at the glass. Walk sideways and the reflection slides the way a reflection slides. Put her in front of it and she is in it: the real her, the pose she is in now, the light she is standing in now.

Because it is a render and not a lookup, everything in your scene is in it. Her hair. Your Lumen Forge beams. The steam. Things behind the camera.

And it costs almost nothing, because it does not redraw every frame

A mirror only has to be as current as your eye can tell. Left on its factory setting the reflection updates on a gate, and on our bench that made it the difference between free and one whole extra render of your scene. There is a table further down with the exact figures and the one rule you have to get right.

There is also a Static mode, which renders once and then stops. For a mirror across the room, nobody has ever noticed.

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Two numbers turn the pane into an arc: an angle and a radius. Take the angle to 360 and it closes into a tube: a shower cylinder, a display column, a container with her inside it. Optional caps top and bottom (the bottom one is off by default, on the grounds that you would step on it).

The curve is real geometry, not a bent texture, so the reflection curves with it: it stretches along the sweep, wraps toward the edges, and does the thing curved glass does where the room smears as it goes round.

The width slider disappears when you switch to curved, because a curve's width is its angle times its radius. It is not hidden. It stopped existing.

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Set the shape to Prism and pick a side count. Three is a triangular column, four is a box, nine is close enough to a cylinder to read as one while still catching light in flat planes.

Then choose how the reflection handles it:

• Faceted: each panel gets its own mirror, aimed by its own normal. Walk past a box and the four faces disagree with each other exactly the way real glass panels do. This is the one that looks expensive.
• Curved: one shared reflection blended across the whole shape, for when you want the prism to read as a cylinder rather than as facets.

Faceted mirrors are ranked by what is actually facing the camera and capped by a budget you set, so a nine-sided prism does not quietly ask for nine renders of your scene.

And every panel is a separate breakable face, so a prism does not shatter as one object. It comes apart a panel at a time.

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Switch on refraction and what is behind the pane stops lining up with what is beside it. An arm crossing the edge of the glass breaks at the boundary and picks up again, offset. Step back and the offset changes. It is the single cheapest way to make a viewer believe there is a physical object in the way, because it is the thing a painted glass texture can never fake.

Physical Refraction scales the effect by the pane's actual thickness, so a 3 mm window barely disturbs anything and a 5 cm slab throws everything sideways. Thickness is a real dimension of the mesh, not a shader constant. Thick glass is thick.

There are two ways to feed it, and the choice matters more than it looks:

• Transmission Camera: a second render of the scene from behind the glass. Correct at any angle, sees things that are off the edge of your screen, and costs a full render.
• Screen Grab: samples what is already on screen. Free, and honestly indistinguishable for a window you look through straight on. It cannot show you what is not on screen, which matters at grazing angles.

There is a genuinely counter-intuitive interaction between refraction and condensation that saves a whole render. It is in the technical section, because nobody would find it by guessing.

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Transparent surfaces in VAM draw in an order, and when two of them disagree you get the classic bug where the fog is in front of the glass from one angle and behind it from another.

Render Queue is a plain slider with the same range VAM's own clothing uses. The default sits at exactly the value the ecosystem pins standard transparent surfaces to, so it composes correctly with water surfaces and volumetric fog out of the box. If you have something unusual, you move it.

Small, unglamorous, and the difference between "these two plugins work together" and "these two plugins fight".

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This is the shower door that Steam Forge was missing. Steam coming off her, water running down her, room fog in the air, and now a pane between you and all of it, fogged from the same heat, with her handprint in it.

They were built to sit next to each other. The render queue slider above is why they compose instead of arguing.

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1. Add an Empty atom
2. Add GlassForge to it
3. There is glass. Move the Empty to place it.

That is the whole setup. Everything below is optional.

• The panel is four tabs (Shape & Look, Optics, Wet, Break), and the tab strip shows a filled dot on any tab that is currently doing something, so you can see the state of the whole plugin without opening it.
• BUILD / REBUILD GLASS and SHATTER are always visible at the top, on every tab.
• Changing width, height, thickness or a curve rebuilds automatically a moment after you stop dragging.
• A control that needs something else switched on stays visible, greys out, and says what would wake it up. Nothing is hidden to keep the panel tidy.
• Every parameter is an ordinary VAM storable, so all of it is drivable from Timeline, triggers, and other plugins.

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Glass is one of the easiest things in a real-time renderer to make expensive, because the obvious implementation renders your scene again for every effect. So this was built around measurement, and several of the design decisions went against the first guess.

Every claim below points at a row. MEASURED is a reading off the bench. DID NOT RESOLVE means the difference was smaller than that comparison's own measured noise, which is not the same as "small", and we are not going to blur the two.

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HONEST NOTES & LIMITS

• VR has no numbers. Every figure on this page is flat-screen, and none of them should be read as applying in VR: a mirror refresh renders once per eye, and a headset's frame rate is low enough that the rate gate crosses fewer of those steps. What exists instead is field observation: GlassForge has been run in VR repeatedly through development with no perceptible stutter or anomaly, including alongside heavy volumetric fog. That answers does it break, which is the question that decides shipping. It does not answer what does it cost, and nothing here pretends otherwise.
• Anti-aliasing 2× vs 4× specifically was never priced. The default is 2, and the whole anti-aliasing axis read flat everywhere it was measured, but no row measures that particular step. That is an argument, not a measurement, and it belongs in this list rather than in the tables.
• More than two cameras was not measured. Two was, and the second one was already the most expensive item on the page.
• Several GlassForge instances in one scene was not measured.
• The fixture room is light on purpose, so costs could be attributed to the thing that caused them. Isolation is the right way to attribute a cost and the wrong way to conclude it is small.
• Screen Grab refraction cannot show what is not on screen. At grazing angles you will see it. That is the trade for it being free.
• Shards are rigid bodies. A few hundred of them in a scene that is already heavy on physics is a physics cost, not a rendering one, and it will not show up in any of the rendering numbers above.

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v1.0
First release.

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Special Thanks

To everyone in the VAM community who keeps building things nobody asked for. And to whoever it was that first put a pane of glass in a scene and then wished they could break it.