Patent ID: 7605811

Claim:
A metaball drawing system comprising: a metaball definition system that defines first and second metaballs with respect to a screen, said respective first and second metaballs being represented by first and second density distributions; a threshold setting system that sets a threshold band with respect to said first and second density distributions; a first metaball determination system that determines whether a pixel on said screen is included in said first metaball; a first density calculation system that calculates a first density at said pixel based on said first density distribution when it is determined that said pixel is included in said first metaball by said first metaball determination system; a first threshold determination system that determines whether said first density falls within said threshold band; a first luminance-value setting system that sets a first luminance value in said pixel based on said first density when it is determined that said first density falls within said threshold band by said first threshold determination system; a second metaball determination system that determines whether said pixel is included in said second metaball after it is determined whether said pixel is included in said first metaball; a second density calculation system that calculates a second density at said pixel based on a density distribution, which is combined by said first and second density distributions, when it is determined that said pixel is included in said second metaball by said second metaball determination system; a second threshold determination system that determines whether said second density falls within said threshold band; and a second luminance-value setting system that sets a second luminance value in said pixel based on said second density when it is determined that said second density falls within said threshold band by said second threshold determination system.