bgfx::setTransform not moving object

[DarthCloud64]

Hello,

Currently, I am rendering this rectangle

I am trying to translate the rectangle down the Y axis when I press down on my keyboard, but it seems like bgfx::setTransform() isn't doing anything. To test, I temporarily changed the code to modify the view matrix based on key down and the camera does look down. Not sure if I'm missing something

cpp code

#include <iostream>
#include <bgfx/bgfx.h>
#include <bx/bx.h>
#include <bx/math.h>
#include <bgfx/platform.h>
#include <GLFW/glfw3.h>

#ifdef _WIN32
#define GLFW_EXPOSE_NATIVE_WIN32 1
#endif

#ifdef __APPLE__
#define GLFW_EXPOSE_NATIVE_COCOA 1
#endif

#ifdef __linux__
#define GLFW_EXPOSE_NATIVE_X11 1
#endif

#include <GLFW/glfw3native.h>

#include "../include/ecs/ComponentStorage.h"
#include "../include/utils/RenderUtils.h"

// The layout is as follows: first 3 elements = vertex position. last 4 elements = vertex color
static const float vertices[] = {
    0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f,   // top right
    0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f,  // bottom right
    -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f, // bottom left
    -0.5f, 0.5f, 0.0f, 1.0f, 0.5f, 0.25f, 1.0f  // top left
};

static const uint16_t indices[] = {
    3, 1, 0, // first triangle
    1, 3, 2  // second triangle
};

static bool movingDown = false;
static void key_callback(GLFWwindow *window, int key, int scanCode, int action, int mods)
{
    if (action == GLFW_PRESS && key == GLFW_KEY_DOWN)
    {
        movingDown = true;
    }
    else
    {
        movingDown = false;
    }
}

static float positionY = 0.0f;

int main()
{
    if (!glfwInit())
    {
        throw std::runtime_error("GLFW failed to initialize\n");
    }

    ComponentStorage componentStorage{};

    glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
    GLFWwindow *window = glfwCreateWindow(1200, 720, "Test", nullptr, nullptr);
    glfwSetKeyCallback(window, key_callback);

    bgfx::Init init;
    init.type = bgfx::RendererType::Vulkan;
    init.platformData.nwh = (void *)glfwGetX11Window(window);
    init.platformData.ndt = glfwGetX11Display();
    init.resolution.width = 1200;
    init.resolution.height = 720;
    init.resolution.reset = BGFX_RESET_VSYNC;
    bgfx::init(init);

    uint8_t red = 154;
    uint8_t green = 100;
    uint8_t blue = 73;
    uint8_t alpha = 255;
    uint32_t rbgaHex = (red << 24) | (green << 16) | (blue << 8) | alpha;
    bgfx::setViewRect(0, 0, 0, uint16_t(1200), uint16_t(720));
    bgfx::setViewClear(0, BGFX_CLEAR_COLOR | BGFX_CLEAR_DEPTH, rbgaHex, 1.0f, 0);

    bgfx::VertexLayout vertexLayout;
    vertexLayout.begin()
        .add(bgfx::Attrib::Position, 3, bgfx::AttribType::Float)
        .add(bgfx::Attrib::Color0, 4, bgfx::AttribType::Float)
        .end();

    Entity triangle = createEntity(componentStorage);
    RenderableComponent renderableComponent{};
    renderableComponent.vertexBufferHandle = bgfx::createVertexBuffer(bgfx::makeRef(vertices, sizeof(vertices)), vertexLayout);
    renderableComponent.indexBufferHandle = bgfx::createIndexBuffer(bgfx::makeRef(indices, sizeof(indices)));
    renderableComponent.shaderProgram = createProgram("/home/rob/Code/C++/conspiracy/build/vertex.bin", "/home/rob/Code/C++/conspiracy/build/fragment.bin");

    while (!glfwWindowShouldClose(window))
    {
        glfwPollEvents();

        float velocity = 0.0f;

        if (movingDown)
        {
            velocity = -1.0f;
        }
        positionY += velocity;

        const bx::Vec3 at = {
            0.0f,
            0.0f,
            0.0f,
        };

        const bx::Vec3 eye = {
            0.0f,
            0.0f,
            -1.0f,
        };

        float viewMatrix[16];
        bx::mtxLookAt(viewMatrix, eye, at);

        float projectionMatrix[16];
        bx::mtxProj(projectionMatrix, 60.0f, 1200.0f / 720.0f, 0.1f, 100.0f, bgfx::getCaps()->homogeneousDepth);

        bgfx::setViewTransform(0, viewMatrix, projectionMatrix);

        const bx::Vec3 modelVector{
            0.0f,
            positionY,
            0.0f,
        };

        float transformationMatrix[16];
        bx::mtxTranslate(transformationMatrix, modelVector.x, modelVector.y, modelVector.z);
        bgfx::setTransform(transformationMatrix);

        bgfx::touch(0);
        bgfx::setVertexBuffer(0, renderableComponent.vertexBufferHandle);
        bgfx::setIndexBuffer(renderableComponent.indexBufferHandle);
        bgfx::setState(BGFX_STATE_DEFAULT);
        bgfx::submit(0, renderableComponent.shaderProgram);

        bgfx::frame();
    }

    bgfx::shutdown();
    glfwDestroyWindow(window);
    glfwTerminate();
    return 0;
}

vertex shader

$input a_position, a_color0
$output v_color0

#include "bgfx_shader.sh"

void main()
{
    v_color0 = a_color0;
    gl_Position = mul(u_modelViewProj, vec4(a_position, 1.0));
}

[bkaradzic]

        bgfx::setTransform(transformationMatrix);

        bgfx::touch(0); // <<---- Move this above bgfx::setTransform call!
        bgfx::setVertexBuffer(0, renderableComponent.vertexBufferHandle);
        bgfx::setIndexBuffer(renderableComponent.indexBufferHandle);
        bgfx::setState(BGFX_STATE_DEFAULT);
        bgfx::submit(0, renderableComponent.shaderProgram);

[DarthCloud64]

Thanks alot. That seems to have fixed the issue. Do you mind providing insight as to why the ordering of when "touch()" is called matters here?

[bkaradzic]

Because bgfx::touch is just special version of bgfx::submit. So everything you set prior to submit gets cleared after submit call.