Shift Rendering Framework

TODO Lists

2024.11.20

• Add UI support!
• Refactor the code, to make right mouse click to add density and left mouse click to add velocity

Note: When mouse clicks then add source, so you should dispatch the add source compute shader when the mouse is clicked, may be that can solve the bug of multiple clicks after releasing the mouse.

• Add the boundary code
• Change the velocity calculation from collocated grid to staggered grid
• Calculate divergence, instead of storing velocity at the center of each cell, stroing the velocity at the edge cell.

Note: check the function ProjectGaussSeidel in FluidSim

• Use horizontal component and vertical component of the velocity instead of using whole vec2
• Finish the velocity component first, including add velocity, advect and project
  • add velocity
  • project
  • advect

2024.11.21

• Need to implement the glfw mouse button callback to make sure glfw send the mouse event to the imgui

2024.11.24

• interpolate the color

2024.11.25

• finish advect function, we can run interpolate in afvect first, then add advect
• add camera movement
• interpolate the velocity after add source

2024.12.03

• volumetric data of isFluid and display it

actually Velocity Field in 3D can be also considered as the volumetric data

• Laid down the 2 dimension one, and add sphere to interact.

Bugs & Questions

2024.11.18

• Multiple click of mouse when try to release the mouse left button

Posible solution: reset the mouse pos which sent to the compute shader to 0 or somevalue after click, 因为这样就不会导致传给compute shader的鼠标位置的值一直固定在我松开鼠标的那个位置。

• The function VelocityProject display black right now

2024.11.20

• 我现在通过一个radius的变量来控制add velocity的范围，如何让鼠标活动影响的程度从重心向radius减小？
• 而且对于速度场来说，在增加速度场的时候，需要使用+= 吗？For example

curVelocityField[index] += vec2(xVel, yVel) + prevVelocityField[index] * deltaTime;
// or
curVelocityField[index] = vec2(xVel, yVel); 

2024.11.21

• Imgui window and glfw window can not communicate, which means they are not in the same context

2024.11.26

• 流体模拟在经过advect之后，会导致全局的velocity field都朝向左下角，也就是x负，y正（向右为x正，向下为y正）

• project的correction太大会导致整个velocity field非常混乱

• 右和上边界是有问题的

• May be I don't need diffuse, I just add noise, it can also save me some performance

So the current steps will be:

• For velocity add source -> project -> advect

• For density add source -> add noise -> advect

2024.11.27

• advect的方向会往比正常方向偏左，检查一下advect中的函数

2024.12.8

• Project在（0，0）点有问题，它会自己在这个点产生未定义的velocity
• Project在四个角都有问题，在velocity为0的情况下他们会自己有本应该是有速度的颜色

Reminder

1. Change the source code of imgui/backends/imgui_impl_glfw.h/cpp because I use the dear-imgui in the 3rdparty of bgfx

2. Change the CMakeLists.txt of the bgfx.cmake to enable shader model 5

FAQ

1. Windows won't pop out in MacOS

• github issue

2. Where should I put my shader files?

3. Attribs which send to vertex shader must be in the following with the exact name, otherwise, it won't send anything to the vertex shader

• vertex shader attribs

4. Enable shader model 5 for d3d

In the file bgfxToolUtils.cmake, comment the line list(APPEND PROFILES s_4_0) inside the function(bgfx_compile_shader), then the system will take shader model 5 as default!

5. Connection between mouse position and gl_FragCoord?

The origin of gl_FragCoord is bottom left, however the origin of glfwGetCursorPos() is top left

6. uniforms

• Uniform structure

If you want to send a struct uniform, for example:

struct uParams {
    float mousePosX;
    float mousePosY;
    int32_t bufferWidth;
    //...
}

Make sure you are using float or int32_t which means each variable should occupy the same amount of memory. double is not allowed, same as int16_t, bool etc.

Note: why float? Cause bgfx force you to use float as the standard variable type of a uniform.

Update on 2024.11.17:

Better only use float, especially when you gonna use the full storage of the unifroms, and also the value that you send to the uniform should also be float, otherwise it may not be sent to the GPU, for example:

struct data {
    // NO! int32_t, better all floats
    float x;
    float y;
    float z;
    float w;
};

void init(data* _data) {
    _data = 0.0f; // the value here should also be float, no int, uint etc.
    // ...
}

• Uniform data

the value you sent to the uniform must be represent as float, which means for example:

_data = 0.0f; // Correct
_data = 0.0;  // false, will be consider as double

7. Framerate issues

I'm not sure why the frame rate in this project changes with the display's maximum refresh rate. For example, with a 60Hz monitor, the frame rate is capped at 60, but when I switch to a 140Hz monitor, it reaches 140. Disabling V-Sync in the NVIDIA control panel under 3D settings unlocks the frame rate limit.

8. .sh file doesn't update after modified it

You should update the shader, for example, add some comments, in order to make the bgfx rebuild the shader.

9. When change some files that are not shader code and are included more than one file, for every shader that include that file, you should change that shader code a little bit to make sure recompile the shader again to apply the changeds.

For example in the fluid simulation shader folder, there is a file call velocity_uniforms.sh which store all the definition of the uniforms, if you change that file, you need to add a tiny change, for instance add a comment, to make sure the shader will be recompiled.