Free online BMP to PLY converter

What the BMP format is

BMP is a bitmap raster format used by Windows Paint, image scanners, screenshots, texture tools, CAD applications, and older rendering software. It stores pixels, usually with 8-bit grayscale, 24-bit RGB, or 32-bit RGBA color; it does not store vertices, polygons, depth, or camera information. BMP files are often uncompressed, which preserves pixel values but makes them larger than PNG or JPEG files.

In 3D work, a grayscale BMP is commonly used as a height map: dark pixels represent low elevation and bright pixels represent high elevation. A normal color photograph contains no reliable depth, so it cannot produce an accurate 3D model without photogrammetry, depth data, or an assumed projection.

What the PLY format is

PLY, also called the Polygon File Format or Stanford Triangle Format, stores 3D model elements such as vertex coordinates, polygon faces, vertex colors, and normals. It is supported by MeshLab, Blender, CloudCompare, Open3D, many 3D scanners, and point-cloud processing tools.

PLY can be ASCII or binary. ASCII is easier to inspect and exchange between programs; binary is smaller and faster for large scans. A PLY generated from one BMP may contain only a colored point cloud or a height-field mesh, not a complete solid model with thickness, watertight boundaries, or physically meaningful scale.

How to actually convert BMP to PLY

Convert a grayscale BMP into a colored point cloud with Python

This method assigns each pixel an X/Y position and converts its brightness into Z height. Install Pillow and NumPy with python -m pip install pillow numpy, then save the following as bmp_to_ply.py:

from PIL import Image
import numpy as np

image = Image.open('input.bmp').convert('RGB')
pixels = np.asarray(image)
gray = np.dot(pixels[..., :3], [0.299, 0.587, 0.114])
height, width = gray.shape
xy_scale = 1.0 / max(width - 1, height - 1)
z_scale = 2.0

with open('output.ply', 'w', encoding='ascii') as out:
    out.write('ply\nformat ascii 1.0\n')
    out.write(f'element vertex {width * height}\n')
    out.write('property float x\nproperty float y\nproperty float z\n')
    out.write('property uchar red\nproperty uchar green\nproperty uchar blue\nend_header\n')
    for row in range(height):
        for col in range(width):
            x = (col - (width - 1) / 2) * xy_scale
            y = ((height - 1 - row) - (height - 1) / 2) * xy_scale
            z = float(gray[row, col]) / 255.0 * z_scale
            r, g, b = pixels[row, col]
            out.write(f'{x} {y} {z} {r} {g} {b}\n')

Run it with python bmp_to_ply.py. The resulting output.ply contains one vertex per pixel and retains the BMP colors. Change z_scale to control relief height; downsample the image first if the source has millions of pixels.

Create a polygon mesh in Blender

1. Open Blender, add a plane, and subdivide it into a grid with approximately the same aspect ratio as the BMP.
2. Create a displacement texture from the BMP through the plane's Modifiers → Add Modifier → Displace controls. Set the texture type to an image or movie, load the BMP, and adjust Strength and Midlevel.
3. Apply the displacement modifier after checking the preview. Add a Solidify modifier only if the exported model needs thickness.
4. Use File → Export → Stanford (.ply), enable vertex colors or normals when needed, and select the desired ASCII or binary encoding.

For a basic browser conversion without installing software, 101convert.com can convert the file for free. Verify the result in a PLY viewer: a generic image-to-geometry conversion still needs a height interpretation, and a flat or invalid model indicates that the source did not contain usable depth information.

Quality, compatibility, and limitations

Pixel dimensions determine geometric resolution, while grayscale precision determines height resolution. An 8-bit BMP provides only 256 height levels, so smooth ramps may show banding; 16-bit height data is preferable when the source supports it.

The Python example creates vertices but no faces, so viewers display a point cloud. A displaced Blender grid creates polygon faces, but its topology follows the image grid and may need decimation, smoothing, or triangulation in MeshLab or Blender. PLY does not automatically preserve BMP metadata, physical units, transparency, layers, or the original image file.

Many PLY readers expect vertex coordinates in a particular unit convention even though PLY itself does not enforce one. Set the X/Y and Z scales deliberately, and confirm whether the receiving application expects vertex colors, normals, triangular faces, ASCII PLY, or binary little-endian PLY.