Setting font color, Vulkan

Question

I am new using Vulkan, and i am trying to learn it looking tutorials and looking the vulkan examples that they provided(vulkan-master: https://github.com/SaschaWillems/Vulkan).

One of them is the Overlaytext project. In this project they teach you how to implement an overlay text in Vulkan.

Using this code, i wanted to change it to add an additional uniform to be able to change the color of the fonts. The problem is that the uniform is not getting set to the color, is always a 0 vec4(0,0,0,0) and i am not getting any warning or error.

If you can please tell me what i am missing i will be really appreciated, i dont know anymore what to do, i am out of ideas.

The code that i added or changed of this project to add this uniform is the following:

Variables in class:

glm::vec4   _color = glm::vec4(1.0f,1.0f,1.0f,1.0f);
struct {
VkBuffer buffer;
VkDeviceMemory memory;

} _colorBuffer;

Input binding and attributes of the pipeline(preparePipeline method):

std::array<VkVertexInputBindingDescription, 3> vertexBindings = {};
vertexBindings[0] = vertexInputBindingDescription(0, sizeof(glm::vec4), VK_VERTEX_INPUT_RATE_VERTEX);
vertexBindings[1] = vertexInputBindingDescription(1, sizeof(glm::vec4), VK_VERTEX_INPUT_RATE_VERTEX);
vertexBindings[2] = vertexInputBindingDescription(2, sizeof(glm::vec4), VK_VERTEX_INPUT_RATE_VERTEX);
std::array<VkVertexInputAttributeDescription, 3> vertexAttribs = {};
// Position
vertexAttribs[0] = vertexInputAttributeDescription(0, 0, VK_FORMAT_R32G32_SFLOAT, 0);
// UV
vertexAttribs[1] = vertexInputAttributeDescription(1, 1, VK_FORMAT_R32G32_SFLOAT, sizeof(glm::vec2));
// Color
vertexAttribs[2] = vertexInputAttributeDescription(2, 2, VK_FORMAT_R32G32B32A32_SFLOAT, 0);

Added starging buffer to copy the content of the color vec4 to a local device buffer(prepareResources method):

struct {
    VkBuffer buffer;
    VkDeviceMemory memory;
} colorStaging;

ErrorCheck(renderer->CreateBuffer(
    VK_BUFFER_USAGE_TRANSFER_SRC_BIT,
    VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT,
    sizeof(glm::vec4),
    &colorStaging.buffer,
    &colorStaging.memory,
    &_color));

ErrorCheck(renderer->CreateBuffer(
    VK_BUFFER_USAGE_VERTEX_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT,
    VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT,
    sizeof(glm::vec4),
    &_colorBuffer.buffer,
    &_colorBuffer.memory));

Copy the staging buffer to the colorBuffer uniform(prepareResources, just after the setImageLayout method and before the end command buffer):

VkBufferCopy copyRegion = {};

copyRegion.size = sizeof(glm::vec4);
vkCmdCopyBuffer(
    copyCmd,
    colorStaging.buffer,
    _colorBuffer.buffer,
    1,
    &copyRegion);

Clean up staging buffer(between stagingBuffer.destroy() and vkFreeCommandBuffers(_device, _command_pool, 1, &copyCmd); in the prepareResources method):

vkDestroyBuffer(renderer->GetVulkanDevice(), colorStaging.buffer, nullptr);
vkFreeMemory(renderer->GetVulkanDevice(), colorStaging.memory, nullptr);

Added the new binding vertex to the update command buffers(update command buffers method, just next to the other bindings):

vkCmdBindVertexBuffers(_commandBuffers[i], 2, 1, &_colorBuffer.buffer, &offsets);

Vertex shader:

#version 450 core

layout (location = 0) in vec2 inPos;
layout (location = 1) in vec2 inUV;
layout (location = 2) in vec4 color;


layout (location = 0) out vec2 outUV;
layout (location = 1) out vec4 outColor;

out gl_PerVertex 
{
    vec4 gl_Position;   
};

void main(void)
{
    gl_Position = vec4(inPos, 0.0, 1.0);
    outUV = inUV;
    outColor = color;
}

Fragment shader:

#version 450 core

layout (location = 0) in vec2 inUV;
layout (location = 1) in vec4 inColor;

layout (binding = 0) uniform sampler2D samplerFont;

layout (location = 0) out vec4 outFragColor;

void main(void)
{
    float color = texture(samplerFont, inUV).r;

    outFragColor = inColor*color;
}

I recompiled both shaders.

If i didnt add something will mean that i didnt change it.

Thank you for attention.

Answer 1

I was trying to use a input vertex instead of a constant push for a vec4. I have changed the implementation to use a constant push and it works.