Planned Graphics Refactor

Discussion in 'Development News' started by RHY3756547, Jan 23, 2015.

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  1. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Currently the graphics rendering in many places is way more intensive than it needs to be. Here are some changes that I'm planning:

    General (replacement static rendering)
    A few things in the game currently implement "static" rendering - however right now that is confined to what is currently on the screen space! This means that when the camera is moved, all the static buffers have to be redrawn anyways, making everything hilariously slow. To solve this for the lot and city, we should be using a scrollable buffer larger than the screen that we only regenerate when it has been exhausted or when a change occurs. This will create a small (maybe 2 frames on older hardware, depending on lot/city complexity) stutter on static buffer regeneration, which isn't great but otherwise you'd be getting a 2 frame stutter on every frame!

    Here's an illustration showing how a static buffer like this works:
    [​IMG]
    You can see that in the red (screen) area, it looks like the crosshatch is smoothly scrolling at 60fps - but this is actually a LIE!! The contents of the scrolling buffer are only re-rendered when the edge is hit.

    Another alternative to this would be to render in many "tile" increments and only rerender tiles that have changed - which is a lot less intensive on the pixel shader but requires a lot more draw calls to render many tiles at once, and calculations to determine which sprites are in which tile.. We'll probably just go for an enlarged single buffer so that the game isn't cpu bound.

    City Rendering
    Right now the city is rendered every frame on all settings. We'll probably want to implement something like the above - even on shadowed mode since the time, and thus the shadows move quite slowly (regen every 1/2 second?). Zooming into or out of the active lot should also have a cool effect, js.

    Vitaboy (Sim Rendering)
    Vitaboy currently re-calculates an avatar's mesh every frame that it is animated. It will be much faster to offload this animation work to the vertex shader, passing in an array of matrices as the bone transforms to calculate the animation on the graphics card, and only pass the original mesh once. Not much will have to be changed from the current implementation, but characters will still need a custom shader to handle the bone transforms.

    Revised vertex format needs:

    POSITION: real vert position
    TEXCOORD0: texture coordinates
    TEXCOORD1: blend vert position
    TEXCOORD2: {x:real vert binding, y: blend vert binding, z: blend vert factor (<=0 means no blend vert)}

    prelim vertex shader:
    Code:
    VitaVertexOut vsVitaboy(VitaVertexIn v){
        VitaVertexOut out;
        float4 position = (1.0-v.params.z) * mul(v.position, SkelBindings[asint(v.params.x)]) + v.params.z * mul(v.bvPosition, SkelBindings[asint(v.params.y)]);
        out.texCoord = v.texCoord;
        out position = mul(v.position, ViewProjection);
        return out;
    }
    
    Lot Sprite Rendering (2DWorldBatch)
    This is currently very inefficient. Right now sprite geometry is regenerated by the cpu for every draw, and the object ID step causes an extra set of draw calls and the aforementioned geometry generation for every object in the update loop!

    What we want is for sprites to instead cache their geometry - positions and all until it changes. Sprite lists can then be built off of the prebuilt geometry, minimizing the per frame impact on the cpu (we could also use geometry shaders to offload this work to the gpu, but it may not be faster), and the projection/view matrix will move instead of the sprites.

    Terrain
    The terrain is a tricky element, since the original game rendered the terrain using the CPU and thus did a few things that we can't easily consider (just drew the blades from the bottom up without any geometry generation or transfer to gfx, just pixel writing), and actually rendered it Z-buffered so that grass could appear over certain elements. I have a few ideas for how this should work, and they all have different pros and cons:

    Grass blades as primitives (current setup)
    [​IMG]

    Right now, if you enable grass blade rendering (currently disabled for performance concerns) this is what you'll get. We basically generate a ton of lines that are the "blades", put them in a graphics buffer, send them to the GFX card and render then whenever needed. As you can probably guess, all of these lines take up a lot of memory, and they take a long time to render.

    Pros:
    • Physically accurate in any render state (2d, 3d, all zoom levels)
    Cons:
    • Very memory intensive!
    • Grass takes a long time to initially generate (took like 5 seconds to generate the grass alone at the volume TSO normally used)
    • Rendering so many primitives is incredibly straining on the rasterizer, so older cards may not be able to keep up

    Flat grass plane with additional grass layers coming out (fur shader style)
    [​IMG]

    This would render the terrain and "overlay" layers floating above the grass that use a PRNG based on the ground's "texture-coord" to draw protruding grass from that position when the PRNG generates a float less than a specified value, which can be altered by how "dead" the grass is or can change depending on which layer is active, to make lower value PRNG grass blades have shorter heights. (would also be affected by how dead grass is, so grass would also be shorter around dead areas!)

    Pros:
    • Incredibly fast, only memory usage for first grass layer..
    • No pre generation
    • Works in 3d!
    • Can make grass sway in wind with vertex shader on layers (future)
    Cons:
    • Risk of severe overdraw - too many grass layers will involve redrawing a portion of the screen layer times, stressing older cards' fillrates. (probably faster than primitives tho)
    • Illusion of a continuous blade will be shattered when zooming in 2x or more, or panning the camera to be near perpendicular to the ground (future).

    Flat grass plane with pixel shader "paralax occlusion map" grass
    Same as above, but work will be moved from the fillrate to the pixel shader - the ground will only render once.

    Pros:
    • No redraw, so potentially faster where fill rate is limited
    Cons:
    • Pixel shader becomes incredibly intensive - Especially if we want to calculate the altered depth of said blades.
    • At edges of the world, grass blades will suddenly cut off.
    • Will not work correctly with bumpy terrain! (not relevant right now, but may be in future.)
    This post is kind of a work in progress right now - i kind of accidentally posted it!
    Last edited: Jan 23, 2015
  2. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Working on vitaboy right now. With the current (old) system this only gets 1 fps on a gaming laptop! (yikes!)
    upload_2015-1-24_18-51-4.png
    JeremyT likes this.
  3. AquilaSim

    AquilaSim Administrator Staff Member Moderator

    OMG! o_O A ARMY OF BOB !!! Shelters !
  4. francot514

    francot514 Well-Known Member

    Why the Bed seems on top of Bob newbie sims, are you drawing z buffer???
  5. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Z buffer restore is currently broken - it's another monogame opengl thing.
  6. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Much faster, but it doesn't quite work yet...
    upload_2015-1-25_4-32-21.png
    Will post an update when the bone matrices are correct.
  7. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    upload_2015-1-25_5-4-18.png
    hehe, works real nice now - I just need to change up 3dworldbatch to optimize for avatars (it is a lot more likely that we will need to send a unique texture for each mesh vs a unique set of bone matrices! there are usually 4+ meshes for each skeleton)

    Runs at about 30 fps with 100 sims on Intel HD Graphics 4000 right now. Special thanks to the power of vertex shaders!
    aidancheddar likes this.
  8. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Working for pets too:
    upload_2015-1-25_5-21-55.png
    Runs at 60fps on NVIDIA, but is unstable for some reason? (random crashes, artifacts on lot load, some avatars flash to a broken state for frames at a time)
    aidancheddar likes this.
  9. francot514

    francot514 Well-Known Member

    All this testing has been done with monogame version??? you had to rewritte the drawing methods and need to change those??
  10. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Uh, sort of?
  11. francot514

    francot514 Well-Known Member

    I want to know what version you have used the monogame port or the xna version, becuase seems youre doing some big changes to lot sprite redering and terrain...
  12. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    This is the monogame port.
  13. Afr0

    Afr0 Well-Known Member

    I will allow you to offload the Vitaboy rendering to shaders, but I'm insisting that we keep the old code in for backward compatibility reasons.
    Eventually I'm going to also write a software renderer for the lot and city rendering (because I hate to have to rely on shaders for everything when the original didn't), but I don't have time now.
    If you can comply with this, I'm all for it! :D
  14. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    The game won't run without at least OpenGL 3.0 at all under monogame. OpenGL 3.0 supports vertex shaders just fine, so for all systems which run monogame we'll have 100% compatability. Most of the vitaboy code will remain the same - It's just the transformation step that has been moved to gfx, making it ~30x faster.
    miceiken and aidancheddar like this.
  15. pisarz1958

    pisarz1958 Administrator Staff Member Moderator

    Great stuff. I hope it'll make PD not run out of video memory (Intel GPU) anymore after running it for some time.
  16. aidancheddar

    aidancheddar Active Member

    Great stuff, Rhys! Lovin' the progress.
  17. SodaDog

    SodaDog Member

    I hope it will be implented!
  18. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    For reasons stated above, a much needed change to make the code make more sense and reduction of data redundancy - the old code is now kaput (still obviously accessible via returning to an older revision). Since MonoGame bottoms out at OpenGL 3.0 support, all cards supporting our game client as is will support these operations.

    Now:
    • Meshes no longer have to be duplicated to bind them to avatars. They all use the same loaded meshes! (saves a lot of memory for 100 avatar case)
    • Meshes no longer contain 2 sets of the same vertices.
    • Drawing is >30x faster! CPU is free(-er) to do more SimAntics processing (not that it's that slow anyways - most of the cpu time is currently wall rendering)
    • Mesh variable names make more sense.
    • Much much more!
    You should still check out the old code for a software implementation though - since it is still accurate.
    aidancheddar likes this.
  19. Afr0

    Afr0 Well-Known Member

    We should branch out the main branch before merging anyway.
  20. RHY3756547

    RHY3756547 FreeSO Developer Staff Member Moderator

    Do you mean tag? Branching out would kind of defeat the whole purpose of merging...
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