Apparatus and method for mip-map generation using low-pass filtering based on resolution ratio

• US 5,566,284 A
• Filed: 12/21/1994
• Issued: 10/15/1996
• Est. Priority Date: 12/22/1993
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Wakayama, Yorihiko
• Primary Examiner(s): Herndon, Heather R.
• Assistant Examiner(s): BUCHEL JR, RUDOLPH JOHN
• Application Number:
  US08/361,209
• Time in Patent Office: 664 Days
• Field of Search: 395/130, 395/162
• US Class Current: 345/587
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

According to the MIP-map image generating apparatus of the invention, an original texture image stored in a memory is processed by spatial transformation in a discrete cosine transform section, so as to be spatial frequency image data. A polygon calculating section calculates the size of a polygon, and calculates resolution ratios of the texture to be mapped. A spatial low-pass filter allows the components of lower frequencies of the spatial frequency image data to pass therethrough using a cutoff frequency corresponding to the resolution ratios of the texture. After the filtered spatial frequency image data is processed by inverse spatial transformation, the size thereof is reduced. Thus, a MIP-map image having a predetermined size is obtained.

Claims

1. An apparatus for MIP-map image generation, which receives an original image of texture and reduces the original image in size in accordance with a size of a polygon to which the texture is mapped, the apparatus comprising:

image dividing means for receiving the original image and for dividing the original image, to generate image blocks;

a spatial transformation means for transforming each of the image blocks in a spatial domain into spatial frequency image block in a spatial frequency domain;

image storing means for storing the spatial frequency image data block;

MIP-map resolution calculating means for calculating a size of a polygon to be displayed on a display, and for calculating a resolution corresponding to the size of the polygon;

low-pass filter means for removing, from the spatial frequency image data block, components having higher frequencies which are higher than a predetermined frequency corresponding to the resolution obtained by the MIP-map resolution calculating means, to generate a filtered spatial frequency image data block; and

inverse spatial transformation means for receiving the filtered spatial frequency image data block, and for transforming the filtered spatial frequency image data block into a filtered image block in the spatial domain.

2. An apparatus for MIP-map image generation according to claim 1, wherein the spatial transformation means transforms each of the image blocks into the spatial frequency image data block by discrete cosine transform, and

wherein the inverse spatial transformation means transforms the filtered spatial frequency image data block into the filtered image block by inverse discrete cosine transform.

3. An apparatus for MIP-map image generation according to claim 1, wherein the image dividing means divides the original image of texture into image blocks, the numbers of the image blocks in a horizontal direction and in a vertical direction being the power of 2.

4. An apparatus for MIP-map image generation, comprising:

image dividing means for receiving an image of texture to be mapped onto a polygon and for dividing the image, to generate image blocks;

spatial transformation means for transforming each of the image blocks in a spatial domain into spatial frequency image block in a spatial frequency domain;

data compression means for compressing the spatial frequency image data block without loss of information, to generate a compressed spatial frequency image data block;

texture image storing means for storing the compressed spatial frequency image data block;

data expansion means for expanding the compressed spatial frequency image data block which is stored in the texture image storing means, to generate a spatial frequency image data block;

MIP-map resolution calculating means for calculating a size of the polygon to be displayed on a display, and for calculating a texture resolution corresponding to the size of the polygon;

low-pass filter means for removing, from the spatial frequency image data block, components having higher frequencies which are higher than a predetermined frequency corresponding to the texture resolution obtained by the MIP-map resolution calculating means, to generate a filtered spatial frequency image data block; and

inverse spatial transformation means for receiving the filtered spatial frequency image data block, and for transforming the filtered spatial frequency image data block into a filtered image block in the spatial domain.

5. An apparatus for MIP-map image generation, which receives original image data representing a 2-dimensional image, and outputs transformed image data representing an image with a size different from that of the 2-dimensional image, the apparatus comprising:

Mip-map resolution calculating means for calculating a resolution ratio of the transformed image data to the original image data;

spatial transformation means for receiving the original image data in a spatial domain, and for transforming the original image data into a spatial frequency image data in a spatial frequency domain, to output the spatial frequency image data;

low-pass filter means for receiving the spatial frequency image data in the spatial frequency domain, and for removing components having frequencies higher than a predetermined frequency corresponding to the resolution ratio obtained by the MIP-map resolution calculating means, to output filtered spatial frequency image data; and

inverse spatial transformation means for receiving and transforming the filtered spatial frequency image data in the spatial frequency domain, and for outputting transformed image data in the spatial domain.

6. A method for MIP-map image generation, for receiving original image data representing a 2-dimensional image, and for outputting transformed image data representing an image with a size different from that of the 2-dimensional image, the method comprising:

a MIP-map resolution calculating step of calculating a resolution ratio of the transformed image data to the original image data;

a spatial transformation step of receiving the original image data in a spatial domain, and of transforming the original image data into a spatial frequency image data in a spatial frequency domain;

a low-pass filtering step of receiving the spatial frequency image data in the spatial frequency domain, and of removing components having frequencies higher than a predetermined frequency corresponding to the resolution ration obtained by the MIP-map resolution calculating step, to output filtered spatial frequency image data; and

an inverse spatial transformation step of receiving the filtered spatial frequency image data in the spatial frequency domain, and of transforming the filtered spatial frequency image data into transformed image data in the spatial domain.

7. A method for MIP-map image generation according to claim 6, further comprising, between the spatial transformation step and the inverse spatial transformation step:

data compressing step of compressing the spatial frequency image data;

data storing step of storing the compressed spatial frequency image data; and

data expanding step of expanding the stored and compressed spatial frequency image data, to obtain spatial frequency image data.