phobos 0.10.0

Fast, powerful Vulkan abstraction library
Documentation 
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//! Utilities for querying acceleration structure build sizes

use anyhow::{bail, Result};
use ash::vk;

use crate::core::device::ExtensionID;
use crate::util::align::align;
use crate::util::to_vk::{AsVulkanType, IntoVulkanType};
use crate::{
    AccelerationStructure, AccelerationStructureBuildInfo, AccelerationStructureBuildType, Device,
};

/// Holds the required sizes of buffers for the acceleration structure
#[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
pub struct AccelerationStructureBuildSize {
    /// Required size of the acceleration structure
    pub size: vk::DeviceSize,
    /// Required size of the scratch buffer for update operations
    pub update_scratch_size: vk::DeviceSize,
    /// Required size of the scratch buffer for build operations
    pub build_scratch_size: vk::DeviceSize,
}

/// Get the build sizes for this acceleration structure build info
pub fn query_build_size(
    device: &Device,
    ty: AccelerationStructureBuildType,
    info: &AccelerationStructureBuildInfo,
    primitive_counts: &[u32],
) -> Result<AccelerationStructureBuildSize> {
    device.require_extension(ExtensionID::AccelerationStructure)?;
    let fns = device.acceleration_structure().unwrap();

    if primitive_counts.len() != info.geometry.geometries.len() {
        bail!(
                "max primitive count length should match the number of geometries (expected: {}, actual: {})",
                info.geometry.geometries.len(),
                primitive_counts.len()
            );
    }

    let sizes = unsafe {
        fns.get_acceleration_structure_build_sizes(
            ty.into_vulkan(),
            &info.geometry.as_vulkan(),
            primitive_counts,
        )
    };
    let scratch_align = device
        .acceleration_structure_properties()?
        .min_acceleration_structure_scratch_offset_alignment
        as vk::DeviceSize;
    Ok(AccelerationStructureBuildSize {
        size: align(sizes.acceleration_structure_size, AccelerationStructure::alignment()),
        update_scratch_size: align(sizes.update_scratch_size, scratch_align),
        build_scratch_size: align(sizes.build_scratch_size, scratch_align),
    })
}