Source Apex Legends — Skeleton ESP Drawing Logic

[byte_corvus]

Finally decided to dump this since I haven't seen a decent skeleton ESP implementation for Apex in ages. This was my personal work-in-progress, and since I moved on from Apex reversing, keeping it in the stash is just wasted space.

Technical Overview
This implementation handles bone matrix iteration and parent-child linkage. It filters out non-essential bone data using standard flags.

// Main loop iteration
for (auto i = 1; i < bone_num; i++)
{
    auto bone_flags = *reinterpret_cast<uint32_t*>(model_ptr + 4 * i + bone_flags_offset);
    auto parent     = *reinterpret_cast<int16_t*>(model_ptr + 2 * i + bone_parent_offset);
    
    // Filtering attachments and invalid bone entries
    if ((bone_flags & 0x100) == 0 || (bone_flags & 0x0003FC00) == 0 || (bone_flags & 0x200) == 0)
        continue;
    if (parent <= 0)
        continue;

    // Projection logic
    if (!WorldToScreen(current_pos, current_bone_screen_pos) || !WorldToScreen(parent_pos, parent_bone_screen_pos))
        continue;
        
    g_render.AddDrawListLine({current_bone_screen_pos.x, current_bone_screen_pos.y},
                             {parent_bone_screen_pos.x, parent_bone_screen_pos.y}, {255, 255, 255, 255});
}

Spoiler: Notes & Warnings

1. Pattern scanning: Using skCrypt for signature obfuscation during runtime offset resolution.
2. Status: The offsets and patterns are dated back to May 2024. They will almost certainly need updating for the current build.
3. Efficiency: The [[unlikely]] branch attributes are used to keep the hot path clean, which is critical for frame latency.

Obviously, don't just copy-paste this blindly. Verify your offsets against the current game dump. If you're building a private internal, this should save you the headache of writing the renderer from scratch.

Anyone else currently working on updating bone matrix structures for the new season?